Tree和XML

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="[url=http://www.adobe.com/2006/mxml]http://www.adobe.com/2006/mxml[/url]" layout="absolute" creati>
<mx:Script>
  <![CDATA[
   [Bindable]
   public var selectedNode:XML; 
   public function treeChanged(event:Event):void
   {
    selectedNode=Tree(event.target).selectedItem as XML;
   }
   public function init():void
   {
    var testArr:Array=new Array(20070301,20080402);
    var testStr:String=testArr.sort().join("");
    var tag:String=testStr.substr(0,4);
    var tag2:String=testStr.substr(4,2);
    var tag3:String=testStr.substr(6,2);
    var reg:RegExp=new RegExp(/(\d{4})(\d{2})(\d{2})/g);
    var moment:String="";
    moment+="<node label=\""+tag+"\">\n"+"  <node label=\""+tag2+"\">\n"+"    <node label=\""+tag3+"\" />\n";
    moment+=testStr.replace(reg,function(s,a,b,c)
    {
     var tt:String="";
     if(tag==a)
     {
      tt+="";
     }else{
      tt+="  </node>\n</node>\n<node label=\""+(tag2="",tag=a)+"\">\n"+"  <node label=\""+(tag2=b)+"\">\n";
     }
     if(b==tag2)
     {
      tt+="";
     }else{
      tt+="  </node>\n  <node label=\""+(tag3="",tag2=b)+"\">\n";
     }
     if(c==tag3)
     {
      tt+="";
     }else{
      tt+="    <node label=\""+(tag3=c)+"\" />\n";
     }
     return tt;
    })
    moment+="  </node>\n</node>\n";
    moment+="";
    var mx:XMLList=new XMLList(moment);
    tree.dataProvider=mx; 
   }
  ]]>
</mx:Script>
<mx:Tree id="tree" x="32" y="64" height="80%" width="150" labelField="@label" change="treeChanged(event)"></mx:Tree> 
<mx:TextArea x="203" y="66" width="150" height="80%" text="[email={selectedNode.@label]{selectedNode.@label[/email]}" />
</mx:Application>

执行后，我点击2007，文本出现2007，我点击01，文本出现01。
我想问的是，用什么方法，可以做到，我点击01，文本出现的是20070301

<mx:TextArea x="203" y="66" width="150" height="80%" text="{selectedNode.parent().parent().@label + selectedNode.parent().@label + selectedNode.@label}"/>