[flexcoders] How to popup a titlewindow in precise position

[j2me_soul]

I have a lot of nested buttons in a vbox. How can I put a popuped titlewindow 
in the center position of the button clicked. 
The codes is:
 <mx:Canvas width="100%" bottom="0">
  <mx:Canvas backgroundImage="@Embed('/assets/background/ButtonBar.png')" 
       width="100%" y="15" height="30" horizontalCenter="0"/>
  <mx:HBox id="ButtonGroup" y="6" horizontalCenter="0">
   <mx:Button id="WorkAlertBtn" label="工作提醒" 
click="workAlert_clickHandler(event)" width="95"/>
   <mx:Button id="IntergratedQueryBtn" label="综合查询" width="95"/>
   <mx:Button id="SummarizeBtn" label="综合概况" width="95"/>
   <mx:Button id="ThematicBtn" label="专题图" width="95"/>
   <mx:Button id="StatisticalAnalysisBtn" label="统计分析" width="95"/>
   <mx:Button id="DocumentBtn" label="电子文档" width="95"/>
   <mx:Button id="ChatBtn" label="交流平台" click="ChatBtn_clickHandler(event)" 
width="95"/>
  </mx:HBox>
...
...