diff --git a/.gitignore b/.gitignore
index 40c0619e..3698b2b5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,6 @@
 node_modules
 .jshintrc
 Procfile
+*.un~
+*.swo
+*.swp
diff --git a/lib/cube/event-expression.js b/lib/cube/event-expression.js
index baaf39e7..4278f61e 100644
--- a/lib/cube/event-expression.js
+++ b/lib/cube/event-expression.js
@@ -120,35 +120,111 @@ module.exports = (function(){
         }
         
         
-        var savedPos0 = pos;
-        var savedPos1 = pos;
-        var result3 = parse__();
-        if (result3 !== null) {
-          var result4 = parse_event_expression();
-          if (result4 !== null) {
-            var result5 = parse__();
-            if (result5 !== null) {
-              var result1 = [result3, result4, result5];
+        var savedPos2 = pos;
+        var savedPos3 = pos;
+        var result10 = parse__();
+        if (result10 !== null) {
+          var result11 = parse_event_expression();
+          if (result11 !== null) {
+            var result12 = parse__();
+            if (result12 !== null) {
+              if (input.substr(pos, 1) === ":") {
+                var result13 = ":";
+                pos += 1;
+              } else {
+                var result13 = null;
+                if (reportMatchFailures) {
+                  matchFailed("\":\"");
+                }
+              }
+              if (result13 !== null) {
+                var result14 = parse__();
+                if (result14 !== null) {
+                  var result15 = parse_event_expression();
+                  if (result15 !== null) {
+                    var result16 = parse__();
+                    if (result16 !== null) {
+                      var result8 = [result10, result11, result12, result13, result14, result15, result16];
+                    } else {
+                      var result8 = null;
+                      pos = savedPos3;
+                    }
+                  } else {
+                    var result8 = null;
+                    pos = savedPos3;
+                  }
+                } else {
+                  var result8 = null;
+                  pos = savedPos3;
+                }
+              } else {
+                var result8 = null;
+                pos = savedPos3;
+              }
             } else {
-              var result1 = null;
-              pos = savedPos1;
+              var result8 = null;
+              pos = savedPos3;
             }
           } else {
-            var result1 = null;
-            pos = savedPos1;
+            var result8 = null;
+            pos = savedPos3;
           }
         } else {
-          var result1 = null;
-          pos = savedPos1;
+          var result8 = null;
+          pos = savedPos3;
         }
-        var result2 = result1 !== null
-          ? (function(expression) { expression.source = input; return expression; })(result1[1])
+        var result9 = result8 !== null
+          ? (function(expression, lock_expression) {
+              var uf = expression.filter;
+              expression.type = lock_expression.type;
+              expression.filter = function(filter) { uf(filter); lock_expression.filter(filter); }; 
+              return expression;
+            })(result8[1], result8[5])
           : null;
-        if (result2 !== null) {
-          var result0 = result2;
+        if (result9 !== null) {
+          var result7 = result9;
         } else {
-          var result0 = null;
-          pos = savedPos0;
+          var result7 = null;
+          pos = savedPos2;
+        }
+        if (result7 !== null) {
+          var result0 = result7;
+        } else {
+          var savedPos0 = pos;
+          var savedPos1 = pos;
+          var result4 = parse__();
+          if (result4 !== null) {
+            var result5 = parse_event_expression();
+            if (result5 !== null) {
+              var result6 = parse__();
+              if (result6 !== null) {
+                var result2 = [result4, result5, result6];
+              } else {
+                var result2 = null;
+                pos = savedPos1;
+              }
+            } else {
+              var result2 = null;
+              pos = savedPos1;
+            }
+          } else {
+            var result2 = null;
+            pos = savedPos1;
+          }
+          var result3 = result2 !== null
+            ? (function(expression) { expression.source = input; return expression; })(result2[1])
+            : null;
+          if (result3 !== null) {
+            var result1 = result3;
+          } else {
+            var result1 = null;
+            pos = savedPos0;
+          }
+          if (result1 !== null) {
+            var result0 = result1;
+          } else {
+            var result0 = null;;
+          };
         }
         
         
diff --git a/lib/cube/event-expression.peg b/lib/cube/event-expression.peg
index 560744f2..b8167387 100644
--- a/lib/cube/event-expression.peg
+++ b/lib/cube/event-expression.peg
@@ -73,7 +73,14 @@
 }
 
 start
-  = _ expression:event_expression _ { expression.source = input; return expression; }
+  = _ expression:event_expression _ ":" _ lock_expression:event_expression _
+{
+    var uf = expression.filter;
+    expression.type = lock_expression.type;
+    expression.filter = function(filter) { uf(filter); lock_expression.filter(filter); }; 
+    return expression;
+  }
+  / _ expression:event_expression _ { expression.source = input; return expression; }
 
 event_expression
   = value:event_value_expression filters:(_ "." _ event_filter_expression)*
diff --git a/lib/cube/metric-expression.js b/lib/cube/metric-expression.js
index c0e15b8d..4553a1af 100644
--- a/lib/cube/metric-expression.js
+++ b/lib/cube/metric-expression.js
@@ -131,35 +131,111 @@ module.exports = (function(){
         }
         
         
-        var savedPos0 = pos;
-        var savedPos1 = pos;
-        var result3 = parse__();
-        if (result3 !== null) {
-          var result4 = parse_metric_additive_expression();
-          if (result4 !== null) {
-            var result5 = parse__();
-            if (result5 !== null) {
-              var result1 = [result3, result4, result5];
+        var savedPos2 = pos;
+        var savedPos3 = pos;
+        var result10 = parse__();
+        if (result10 !== null) {
+          var result11 = parse_metric_additive_expression();
+          if (result11 !== null) {
+            var result12 = parse__();
+            if (result12 !== null) {
+              if (input.substr(pos, 1) === ":") {
+                var result13 = ":";
+                pos += 1;
+              } else {
+                var result13 = null;
+                if (reportMatchFailures) {
+                  matchFailed("\":\"");
+                }
+              }
+              if (result13 !== null) {
+                var result14 = parse__();
+                if (result14 !== null) {
+                  var result15 = parse_event_expression();
+                  if (result15 !== null) {
+                    var result16 = parse__();
+                    if (result16 !== null) {
+                      var result8 = [result10, result11, result12, result13, result14, result15, result16];
+                    } else {
+                      var result8 = null;
+                      pos = savedPos3;
+                    }
+                  } else {
+                    var result8 = null;
+                    pos = savedPos3;
+                  }
+                } else {
+                  var result8 = null;
+                  pos = savedPos3;
+                }
+              } else {
+                var result8 = null;
+                pos = savedPos3;
+              }
             } else {
-              var result1 = null;
-              pos = savedPos1;
+              var result8 = null;
+              pos = savedPos3;
             }
           } else {
-            var result1 = null;
-            pos = savedPos1;
+            var result8 = null;
+            pos = savedPos3;
           }
         } else {
-          var result1 = null;
-          pos = savedPos1;
+          var result8 = null;
+          pos = savedPos3;
         }
-        var result2 = result1 !== null
-          ? (function(expression) { return expression; })(result1[1])
+        var result9 = result8 !== null
+          ? (function(expression, lock_expression) { 
+              var uf = expression.filter; 
+              expression.type = lock_expression.type;
+              expression.filter = function(filter){ uf(filter); lock_expression.filter(filter); }; 
+              return expression; 
+            })(result8[1], result8[5])
           : null;
-        if (result2 !== null) {
-          var result0 = result2;
+        if (result9 !== null) {
+          var result7 = result9;
         } else {
-          var result0 = null;
-          pos = savedPos0;
+          var result7 = null;
+          pos = savedPos2;
+        }
+        if (result7 !== null) {
+          var result0 = result7;
+        } else {
+          var savedPos0 = pos;
+          var savedPos1 = pos;
+          var result4 = parse__();
+          if (result4 !== null) {
+            var result5 = parse_metric_additive_expression();
+            if (result5 !== null) {
+              var result6 = parse__();
+              if (result6 !== null) {
+                var result2 = [result4, result5, result6];
+              } else {
+                var result2 = null;
+                pos = savedPos1;
+              }
+            } else {
+              var result2 = null;
+              pos = savedPos1;
+            }
+          } else {
+            var result2 = null;
+            pos = savedPos1;
+          }
+          var result3 = result2 !== null
+            ? (function(expression) { return expression; })(result2[1])
+            : null;
+          if (result3 !== null) {
+            var result1 = result3;
+          } else {
+            var result1 = null;
+            pos = savedPos0;
+          }
+          if (result1 !== null) {
+            var result0 = result1;
+          } else {
+            var result0 = null;;
+          };
         }
         
         
diff --git a/lib/cube/metric-expression.peg b/lib/cube/metric-expression.peg
index 80aa9bcf..789a9e6e 100644
--- a/lib/cube/metric-expression.peg
+++ b/lib/cube/metric-expression.peg
@@ -104,7 +104,14 @@
 }
 
 start
-  = _ expression:metric_additive_expression _ { return expression; }
+  = _ expression:metric_additive_expression _ ":" _ lock_expression:event_expression _ 
+{ 
+    var uf = expression.filter; 
+    expression.type = lock_expression.type;
+    expression.filter = function(filter){ uf(filter); lock_expression.filter(filter); }; 
+    return expression; 
+  }
+  / _ expression:metric_additive_expression _ { return expression; }
 
 metric_additive_expression
   = head:metric_multiplicative_expression tail:(_ additive_operator _ metric_additive_expression)* { return compoundMetric(head, tail); }
diff --git a/package.json b/package.json
index 3991731e..dea5fd0c 100644
--- a/package.json
+++ b/package.json
@@ -18,7 +18,7 @@
   "dependencies": {
     "mongodb": "~1.3.18",
     "node-static": "0.6.5",
-    "pegjs": "0.7.0",
+    "pegjs": "0.6.2",
     "vows": "0.7.0",
     "websocket": "1.0.8",
     "websocket-server": "1.4.04"
diff --git a/test/event-expression-test.js b/test/event-expression-test.js
index 9f12a79b..d14bcd6d 100644
--- a/test/event-expression-test.js
+++ b/test/event-expression-test.js
@@ -236,8 +236,18 @@ suite.addBatch({
       parser.parse("test.in(i, [\"foo\", 42])").filter(filter);
       assert.deepEqual(filter, {"d.i": {$in: ["foo", 42]}});
     }
+  },
+  "lock expression": {
+    "lock expression merges additional filters": function() {
+      var filter = {};
+      parser.parse("test.gt(i, 42):test.le(i, 52)").filter(filter);
+      assert.deepEqual(filter, {"d.i": {$gt: 42, $lte: 52}});
+    },
+    "lock expression results in expected type": function() {
+      var e = parser.parse("test1.gt(i, 42):test.le(i, 52)");
+      assert.equal(e.type, "test") 
+    }
   }
-
 });
 
 suite.export(module);
diff --git a/test/metric-expression-test.js b/test/metric-expression-test.js
index 0fd39844..ea7ac708 100644
--- a/test/metric-expression-test.js
+++ b/test/metric-expression-test.js
@@ -5,7 +5,7 @@ var vows = require("vows"),
 var suite = vows.describe("metric-expression");
 
 suite.addBatch({
-
+  
   "a simple unary expression, sum(test)": {
     topic: parser.parse("sum(test)"),
     "is unary (has no associated binary operator)": function(e) {
@@ -295,9 +295,19 @@ suite.addBatch({
       var filter = {};
       parser.parse("sum(test.in(i, [\"foo\", 42]))").filter(filter);
       assert.deepEqual(filter, {"d.i": {$in: ["foo", 42]}});
+    },
+  },
+  "lock expression": {
+    "lock expression merges additional filters": function() {
+      var filter = {};
+      parser.parse("sum(test.gt(i, 42)):test.le(i, 52)").filter(filter);
+      assert.deepEqual(filter, {"d.i": {$gt: 42, $lte: 52}});
+    },
+    "lock expression results in expected type": function() {
+      var e = parser.parse("sum(test1.gt(i, 42)):test.le(i, 52)");
+      assert.equal(e.type, "test") 
     }
   }
-
 });
 
 suite.export(module);