[flexcoders] How to using the slider to control VideoDisplay?

[underyang]

   hi,all. I'm so tired test my video app.When i click button play or 
button another play,The APP is ok,no problem. But when i drag the 
slider thumb ,the question is coming.The videoDisplay playheadTime 
can't adjusted.  How to solves this problem? Thank you for answer to 
me.
There is a sample example.
 
========================================================
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"; 
layout="absolute"
         >
<mx:Script>
        <![CDATA[
                import mx.controls.videoClasses.VideoError;
                import mx.events.SliderEvent;
                import mx.events.VideoEvent;
                import mx.controls.Alert;
                
         
                private function mover(event:VideoEvent):void{
                    hs.value = flvideo.playheadTime;
                     hs.maximum=flvideo.totalTime;
                         
                }
                
                private function changeHandler
(event:SliderEvent):void{
                        flvideo.playheadTime = hs.value;
                }                
        ]]>
</mx:Script>
        <mx:VideoDisplay id="flvideo" playheadUpdate="mover
(event)"  x="31" y="36" width="345" height="232"/>
                 
  <mx:Button click="flvideo.source='xxx111.flv'" x="67.5" y="295" 
label="play"/>
  <mx:HSlider  minimum="0"  id="hs"  change="changeHandler(event)"  
x="31" y="275"/>
  <mx:Button x="171" y="295" label="Another Play" 
click="flvideo.source='xxx222.flv'"/>
</mx:Application>