[flexcoders] How could I get the index of tree when use XMLList as dataProvider?

[George]

Hi guys,

I'm going to find the index of an item from tree list, then use that 
index as .selectedIndex of tree, to highlight that item. The 
dataProvider I used for the tree like this:

this._source = <list>
                <node label="A" data="a">
                    <node label="A1" data="a1"/>
                    <node label="A2" data="a2"/>
                    <node label="A3" data="a3">
                        <node label="A4" data="a4"/>
                    </node>
                </node>
                <node label="B" data="b">
                    <node label="B1" data="b1">
                    </node>
                </node>
            </list>;

[Bindable]
public var sourceTree:XMLList;
<mx:Tree id="list" dataProvider="{this.sourceTree}" />

public function reselectItemFromData(data:String):void
{
          var treeList:XMLList =this.list.dataProvider as XMLList;
         //TODO: find the index here.
 }

So I want to reselect an item with @data value, i.e. 
reselectItemFromData('b'). Should I go through the _source XML and find 
the index of 'B' item and use that integer as .selectedIndex(not quite 
sure correct or not), or there's a better way on this?

Any help appreciated.

Thanks,
George