Flex: linking dataProvider with custom itemRenderer in a DataGrid

I开发者_运维知识库m working at a DataGrid which has a custom itemRenderer with a checkbox and a Label inside. Im struggling adding the the values from a xml to the wright label dynamically... how can I make the connection from the datagrid's dataProvider (a xml doc) to the label and the checkbox? My itemRenderer loks a following:

<mx:Component id="ChoiceRenderer">
<mx:HBox width="100%" height="100%" horizontalAlign="center" verticalAlign="middle" horizontalScrollPolicy="off">
    <mx:CheckBox/>
    <mx:Label  />
</mx:HBox>

Thanks for any hint! Markus

Given the XML

<a>
    <b>
    </b>
</a>

acces the contents of <b> e.g. by

<mx:Label text="{data.a.b}"/>