Flex 2 : How to call java function

Hi

Please can someone help me to fix the issue on how to call the javascript function from my flex apps, below the code i have and not sure whats going wrong:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute"
  xmlns:kdwn="ActionScript.*"
  creationComplete="initApp();">
<mx:Script> 
  <![CDATA[
  import mx.formatters.DateFormatter;
  import mx.controls.dataGridClasses.DataGridColumn;
  import mx.formatters.NumberFormatter;
  import mx.collections.XMLListCollection;
  import mx.messaging.channels.RTMPChannel;
  import mx.managers.PopUpManager;
  import mx.collections.ArrayCollection;
  import mx.events.ListEvent;
  import mx.events.MenuEvent;
  import mx.rpc.events.ResultEvent;
  import mx.rpc.events.FaultEvent;
  import mx.utils.ArrayUtil;
  import mx.controls.Alert;
  import flash.events.EventDispatcher;
  import mx.validators.*;
  import mx.controls.Menu;
  import flash.net.LocalConnection;
  import mx.modules.*;

  private function initApp():void
  {
  this.addEventListener(KeyboardEvent.KEY_DOWN, trapKeys);
  this.addEventListener(KeyboardEvent.KEY_UP, trapKeys);
  }

  private function trapKeys(event:KeyboardEvent):void
  {
  Alert.show("key pressed");
  }
  ]]>
</mx:Script> 
<mx:VBox x="0" y="0" height="771" width="1085">
  <mx:Text text="&quot;CTRL+S&quot; to Save" width="168" fontThickness="4" fontWeight="bold" fontSize="16"/>
</mx:VBox>

in my index.template.html i have include the function as below:

<script language="JavaScript"  type="text/javascript">

function FocusOn()

{ Alert("Focus on");

   document.getElementById("focus").focus();

}

</script>

yet unable to call it....any inputs to fix this please?