title: Accessing an ItemRenderer in a DataGrid
body: <p>I have a data grid that has a checkbox item renderer in a cloumn to allow row selections:</p>
  
  <p><strong>Main application:</strong></p>
  
  <pre>
  <code>
  &lt;mx:DataGrid id="dg">
      &lt;mx:columns>
          &lt;mx:DataGridColumn id="ir" itemRenderer="renderers.RowCheckbox" /> 
          &lt;mx:DataGridColumn dataField="Name" headerText="Name" /> 
      &lt/mx:columns>
  &lt;/mx:DataGrid>
  </code>
  </pre>
  
  <p><strong>Item renderer:</strong></p>
  
  <pre>
  <code>
  &lt;-- RowCheckbox -->
  &lt;?xml version="1.0" encoding="utf-8"?>
  &lt;mx:HBox xmlns:mx="http://www.adobe.com/2006/mxml" horizontalAlign="center"> 
      &lt;mx:CheckBox id="chk"/>
  &lt;/mx:HBox>
  </code>
  </pre>
  
  <p>How can I get a handle to the item renderer / checkbox so that I may determine which rows are checked?</p>