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

[underyang]

HI all,I'm so tired tested a video app.here is a sample.ActionScript 
is:

======================================================
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"; 
layout="absolute">
<mx:Script>
        <![CDATA[
                import mx.events.SliderEvent;
                import mx.events.VideoEvent;
         
         
                 
                private function mover(event:VideoEvent):void{
                         trace(flvideo.playheadTime);
                         hs.value = flvideo.playheadTime;
                         hs.maximum=flvideo.totalTime;
                }
                
                private function changeHandler
(event:SliderEvent):void{
                        flvideo.playheadTime = event.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="NO1"/>
  <mx:HSlider  minimum="0"  id="hs"  change="changeHandler(event)"  
x="31" y="275"/>
  <mx:Button x="171" y="295" label="NO2" 
click="flvideo.source='XXX222.flv'"/>
</mx:Application>

=================================================
    When I click Button to play xxx111.flv, have noquestion.But,When 
i change slider and click another button to play xxx222.flv,the 
question is happen.Slider's value is wrong.How can I solve this 
problem?
    sorry for my english.