flex return rowIndex from button in datagrid component

flex return rowIndex from button in datagrid component

Hi I am trying to pass the rowindex when I click on a button in a row, the
data value returns the correct information but the rowIndex returns
nothing.
<mx:AdvancedDataGridColumn headerText="EDIT" showDataTips="false"
editable="true">
<mx:itemRenderer>
<fx:Component>
<mx:HBox horizontalAlign="center" verticalAlign="middle">
<s:Button label="Edit" id="editGeo"
click="{outerDocument.onClick(data, rowIndex)}"/>
</mx:HBox>
</fx:Component>
</mx:itemRenderer>
</mx:AdvancedDataGridColumn>
thanks !