[flexcoders] Column with custom renderer does not have underlying data

[markgoldin_2000]

Here is my dataGrid:
mx:DataGrid height="212" enabled="true" id="blockTrackDetails" 
verticalScrollPolicy="on" 
                rowHeight="22" width="100%" 
itemClick="rowSelected(event)">
                <mx:columns>
                        <mx:DataGridColumn headerText="Track" 
dataField="tcrctk"/>
                        <mx:DataGridColumn headerText="Cars #" 
dataField="carnumber"/>
                        <mx:DataGridColumn headerText="Loads" 
dataField="loads"/>
                        <mx:DataGridColumn headerText="empty" 
dataField="empty"/>
                        <mx:DataGridColumn headerText="Tons" 
dataField="tons"/>
                        <mx:DataGridColumn headerText="Feet" 
dataField="feet"/>
                        <mx:DataGridColumn headerText="Reassign To" 
dataField="newtrain"/>
                        <mx:DataGridColumn headerText="" 
dataField="tcbkcd" visible="false"/>
                </mx:columns>
        </mx:DataGrid>

Setting custom renderer for column #7:
                var reAssignBlocks:ClassFactory = new 
ClassFactory(reassignBlocksRenderer);                   
                var reAssignBlocksColumn:DataGridColumn = 
blockTrackDetail(params.popupWindow).blockTrackDetails.columns[6];
                reAssignBlocks.properties = {dataProvider : 
resultXML.trainlist.train_symbol};
                        reAssignBlocksColumn.itemRenderer = 
reAssignBlocks;

custom renderer data change:
public function handleDataChanged(event:ListEvent):void 
                {       
                        var colName:String = 
DataGrid(listData.owner).columns[listData.columnIndex].dataField;
                        data[colName] = selectedItem.data;
                        trace(DataGrid(listData.owner).selectedItem);
        }
trace does not show newtrain field at all.

At a time of assigning data to dataGrid that field is shown by a 
trace. Please help.

Thanks