How to Handle GP Tool Execution Result Asynchronously in ArcEngine with Background 64bit

[Aqulia]

I am using ArcEngine with background 64bit and calling GP tools using the ExecuteAsync event. I want to continue processing the results of the GP tool execution after it finishes. Following the official example of gp.ToolExecuted to monitor the execution status of the GP tool, I noticed that the event within gp.ToolExecuted is triggered only after the main function completes. How can I modify my code to handle the GP tool's results immediately after execution, without waiting for the main function to finish?
`private async void btnRunGP_Click(object sender, EventArgs e)
{
try
{
#region tidy up any previous gp runs
//Clear the ListView control
listView1.Items.Clear();
//Remove any result layers present in the map
IMapLayers mapLayers = axMapControl1.Map as IMapLayers;
foreach (IFeatureLayer resultLayer in _resultsList)
{
mapLayers.DeleteLayer(resultLayer);
}
axTOCControl1.Update();

    _resultsList.Clear();
    
    _myGPToolsToExecute.Clear();
    #endregion
    ESRI.ArcGIS.AnalysisTools.Buffer bufferTool = new ESRI.ArcGIS.AnalysisTools.Buffer();
    bufferTool.in_features = _layersDict["Cities"];
    bufferTool.buffer_distance_or_field = txtBufferDistance.Text + " Miles";
    bufferTool.out_feature_class = "city_buffer.shp";
    ESRI.ArcGIS.AnalysisTools.Clip clipTool = new ESRI.ArcGIS.AnalysisTools.Clip();
    clipTool.in_features = _layersDict["ZipCodes"];
    clipTool.clip_features = bufferTool.out_feature_class;
    clipTool.out_feature_class = "city_buffer_clip.shp";
    _myGPToolsToExecute.Enqueue(bufferTool);
    _myGPToolsToExecute.Enqueue(clipTool);
     _gp.ExecuteAsync(_myGPToolsToExecute.Dequeue());
    //I want to do something after executeAsync,but I dont want to put them in ToolExecuted
    MessageBox.show("finish")

}
catch (Exception ex)
{
    listView1.Items.Add(new ListViewItem(new string[2] { "N/A", ex.Message }, "error"));
}

}
void _gp_ToolExecuted(object sender, ToolExecutedEventArgs e)
{
IGeoProcessorResult2 gpResult = (IGeoProcessorResult2)e.GPResult;

try
{
    //The first GP tool has completed, if it was successful process the others
    if (gpResult.Status == esriJobStatus.esriJobSucceeded)
    {
        listView1.Items.Add(new ListViewItem(new string[2] { "ToolExecuted", gpResult.Process.Tool.Name }, "success"));

        //Execute next tool in the queue
        if (_myGPToolsToExecute.Count > 0)
        {
            _gp.ExecuteAsync(_myGPToolsToExecute.Dequeue());
        }
        //If last tool has executed add the output layer to the map
        else
        {
            IFeatureClass resultFClass = _gp.Open(gpResult.ReturnValue) as IFeatureClass;
            IFeatureLayer resultLayer = new FeatureLayerClass();
            resultLayer.FeatureClass = resultFClass;
            resultLayer.Name = resultFClass.AliasName;

            //Add the result to the map
            axMapControl1.AddLayer((ILayer)resultLayer, 2);
            axTOCControl1.Update();

            //add the result layer to the List of result layers
            _resultsList.Add(resultLayer);
        }
    }
    //If the GP process failed, do not try to process any more tools in the queue
    else if (gpResult.Status == esriJobStatus.esriJobFailed)
    {
        //The actual GP error message will be output by the MessagesCreated event handler
        listView1.Items.Add(new ListViewItem(new string[2] { "ToolExecuted", gpResult.Process.Tool.Name + " failed, any remaining processes will not be executed." }, "error"));
        //Empty the queue
        _myGPToolsToExecute.Clear();
    }
}
catch (Exception ex)
{
    listView1.Items.Add(new ListViewItem(new string[2] { "ToolExecuted", ex.Message }, "error"));
}

}`