how to attach an action listener to a drop down menu

[mvreddy.madhu]

hello,
         in my custmerList.xhtml file there is a drop down,after selecting the value here i want to attach the action listener to validate the unique key.can any body suggest me how to attach an action listener to drop down menu.
  there is a sample of code here thats not working.



<s:decorate id="appFunctionField" template="layout/edit.xhtml">
    <ui:define name="label">#{messages['toms.application.properties.Function_code']}</ui:define>
       <h:selectOneMenu value="#{appRoleFunctionHome.instance.appFunction}" required="true" id="appFunction">
                <s:selectItems value="#{appFunctionList.resultList}" var="appFunction" label="#{appFunction.id.functionCode}" noSelectionLabel="#{messages['toms.application.messages.Please_select']}"/>

<a4j:support id="functionCodeField" event="onblur"
                        reRender="functionCodeField" ajaxSingle="true"
                      actionListener="#{appFunctionHome.verifyCarrierCodeAvailable}"/>
  <s:convertEntity />
   </h:selectOneMenu>
       </s:decorate>

[marcioendo.marcioendo.gmail.com]

<a4j:support 
   id="functionCodeField" 
   event="onblur"
   reRender="functionCodeField" 
   ajaxSingle="true"
   actionListener="#{appFunctionHome.verifyCarrierCodeAvailable}"/>

Does it work if you try the onchange event instead?

[nepoez.nepoez.gmail.com]

onchange works for sure.  worse come to worse, there's a silly way around it which is a javascript onchange that will click a hidden commandbutton heehee.  Try onchange, it should work