how Filter XML data by Flash Builder

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/halo" minWidth="1024" minHeight="768"
creationComplete="init1()">
<fx:Script>
<![CDATA[
import mx.collections.XMLListCollection;
import mx.controls.Alert;
import mx.rpc.events.FaultEvent;
import mx.rpc.events.ResultEvent;
[Bindable]
public var employeeData:XMLListCollection=new XMLListCollection();
public function init1():void
{
sendReport.send();
}
public function resultHandler(event:ResultEvent):void
{
var employeeResultData:XMLList=new XMLList();
employeeResultData=event.result.employee;
employeeData.source=employeeResultData;
}
public function faultHandler(event:FaultEvent):void
{
mx.controls.Alert.show("e");
}
private function filterEmployees(item:XML):Boolean
{
var searchResult:XMLList=new XMLList();
searchResult=item.(firstname==searchTerm.text||lastname==searchTerm.text);
if(searchResult.length()>0)
{
return true;
}
else
{
return false;
}
}
public function enterHandler():void
{
if(searchTerm.text!="")
{
employeeData.filterFunction=filterEmployees;
}
else
{
employeeData.filterFunction=null;
}
employeeData.refresh();
}
]]>
</fx:Script>
<fx:Declarations>
<s:HTTPService id="sendReport" result="resultHandler(event)"
fault="faultHandler(event)"
url="Data/employees.xml" resultFormat="e4x"/>
</fx:Declarations>
<mx:AdvancedDataGrid x="78" y="104" id="adg1" designViewDataType="flat"
dataProvider="{employeeData}">
<mx:columns>
<mx:AdvancedDataGridColumn headerText="First Name" dataField="firstname"/>
<mx:AdvancedDataGridColumn headerText="Last Name" dataField="lastname"/>
</mx:columns>
</mx:AdvancedDataGrid>
<s:TextInput x="78" y="74" width="302" id="searchTerm" enter="enterHandler()"/>
</s:Application>
//////////////XML FILE in SRC/data/employees.xml///////////////
<employees>
<employee>
<firstname>MUHAMMAD</firstname>
<lastname>IMRAN</lastname>
<id>DSC02305</id>
<title>prsident</title>
</employee>
<employee>
<firstname>MUHAMMAD</firstname>
<lastname>abbas</lastname>
<id>DSC0230688</id>
<title>student</title>
</employee>
<employee>
<firstname>MUHAMMAD</firstname>
<lastname>asif</lastname>
<id>DSC02309</id>
<title>minister</title>
</employee>
</employees>