[flexcoders] advancedDataGridColumn.styleFunction question

[MicC]

private function formatSummary(data:Object,
col:AdvancedDataGridColumn):Object
{
   if (data.hasOwnProperty("summary"))
   {
      return { color:0xFF0000, fontWeight:"bold",
      textAlign:"right" };
   }
                        
   return {};
}

<mx:AdvancedDataGridColumn headerText = "PI"  textAlign="right"
labelFunction="formatIntADG" dataField="pirevenue"
styleFunction="formatSummary"/>

This works perfectly and formats my grid summary rows in red, bold text. But 
advancedDataGridColumn also has Styles: backgroundColor="0x......" with which I 
was hoping to shade all my summary rows e.g. grey - has no effect. Should it? 
TIA,

Mic.