[flexcoders] Access FormItem child

[markgoldin_2000]

If I have a FormItem like this:
<?xml version="1.0" encoding="utf-8"?>
<mx:FormItem xmlns:mx="http://www.adobe.com/2006/mxml"; 
        width="100%" height="100%" direction="horizontal">
        <mx:TextInput id="username"/>  
        <mx:Button width="22" icon="@Embed(source='../assets/find.png')" 
id="find">             
        </mx:Button>
</mx:FormItem>

then in another mxml fil where I am using that component:
<userLookUp>                    
</userLookUp>

is there a way of accessing username via markup tags? Or it's only via AS?

Thanks