Flex 如何实现用List组件做滚动广告牌

实现的效果：中间每隔几秒就向上反动一下滚动广告。当鼠标悬停在广告上时，滚动条不在滚动，点击广告可以链接到其他地方。
下面是核心代码部分：

<?xml version="1.0" encoding="utf-8"?>
<s:ItemRenderer xmlns:fx="http://ns.adobe.com/mxml/2009" 
                xmlns:s="library://ns.adobe.com/flex/spark" 
                xmlns:mx="library://ns.adobe.com/flex/mx">


        <fx:Script>
           <![CDATA[
import flash.net.navigateToURL;

            [Bindable]
private var title:String;

            [Bindable] 
private var link:String;

            override public function set data(value:Object):void{
super.data = value;
                this.title = value.title;
                this.link = value.link;
                invalidateDisplayList();
            }

            protected function clickHandler(event:MouseEvent):void
            {
// TODO Auto-generated method stub
                navigateToURL(new URLRequest(this.link),'_blank');   
            }

        ]]>
    </fx:Script>
        <mx:LinkButton label="{title}" click="clickHandler(event)" width="240" />        
</s:ItemRenderer>

下面是List的itemrenderer部分:

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <s:BorderContainer xmlns:fx="http://ns.adobe.com/mxml/2009" 
 3           xmlns:s="library://ns.adobe.com/flex/spark" 
 4           xmlns:mx="library://ns.adobe.com/flex/mx" width="100%"
 5           creationComplete="creationCompleteHandler(event)"
 6               horizontalCenter="0" borderVisible="false">
 7     <fx:Script>
 8         <![CDATA[
 9             
10             import mx.events.FlexEvent;
11             
12             private var timer:Timer;
13             private var PreListy:Number;//记录list移动之前的y坐标
14             
15             private var afterListy:Number;  //移动之后的list的y坐标
16             
17             protected function creationCompleteHandler(event:FlexEvent):void
18             {
19                 timer=new Timer(3000);
20                 timer.addEventListener(TimerEvent.TIMER,onTimer);
21                 timer.start();
22                 PreListy=promotionList.y;//记录list向上移动之前的y坐标
23             }
24             
25             private function onTimer(event:TimerEvent):void
26             {        
27                 move_up.yFrom=promotionList.y;
28                 move_up.yTo=promotionList.y-25;
29                 move_up.play();
30                 afterListy=promotionList.y;    
31                 var i:Number=PreListy-afterListy        
32                 if(i>=40)
33                 {
34                     change();  //移动到原来的位置
35                 }  
36             }
37 
38             private function change():void
39             {    
40                 move_up.yFrom=promotionList.y;
41                 move_up.yTo=promotionList.y+50;
42                 move_up.play();
43             }
44             
45             private function move_pause():void
46             {
47                 move_up.pause();
48                 timer.stop();
49             }
50             private function move_resume():void
51             {
52                 move_up.resume();
53                 timer.start();
54             } 
55             
56         ]]>
57     </fx:Script>
58 
59     <s:BorderContainer height="50" backgroundColor="#00eeeeee">
60         <s:List >68 </s:BorderContainer>