Flex 4 ~ enable Group scroll

<s:Scroller  x="355" y="150"  width="600" height="440" horizontalScrollPolicy="off" >
<s:Group  id="ContentWrapper"   >
</s:Group>
</s:Scroller>

reference
http://help.adobe.com/en_US/flex/using/WS03d33b8076db57b9466e6a52123e854e5d5-8000.html