statement_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
<data>

         <record id="statement_st_completion_rule_view_form" model="ir.ui.view">
             <field name="name">account.statement.completion.rule.view (account_statement_regex_account_completion)</field>
             <field name="model">account.statement.completion.rule</field>
             <field name="inherit_id" ref="account_statement_base_completion.statement_st_completion_rule_view_form" />
             <field name="arch" type="xml">
                <field name="function_to_call" position="after">
                    <group colspan="2">
                        <field name="regex" attrs="{'invisible':[('function_to_call','!=','set_account')],'required':[('function_to_call','=','set_account')]}"/>
                        <field name="account_id" attrs="{'invisible':[('function_to_call','!=','set_account')],'required':[('function_to_call','=','set_account')]}"/>
                    </group>
                </field>
             </field>
         </record>

</data>
</openerp>