[flexcoders] Access Checkbox ItemRenderer in AdvancedDataGrid

[Matthew]

Hi - 

I have a button outside an AdvancedDataGrid. On the click event, I want to find 
which of my checkbox item renderers are selected. For some reason, I can't 
figure out. Here's my code below. Any tips are greatly appreciated. 

Thank you!

<mx:Button label="Remove Selections" click="removeGrouping();" />
        <mx:AdvancedDataGrid
                id="GroupingGrid"
                width="100%"
                height="45%">
                <mx:dataProvider>
                        <mx:HierarchicalData source="{model.groupingColl}" />
                </mx:dataProvider>
                <mx:columns>
                        <mx:AdvancedDataGridColumn textAlign="center" 
dataField="label"  headerText="Group"/>
                        <mx:AdvancedDataGridColumn textAlign="center" 
dataField="cpName" headerText="CP Name" />
                        <mx:AdvancedDataGridColumn textAlign="center" 
dataField="parentId" headerText="Parent ID" />
                        <mx:AdvancedDataGridColumn textAlign="center" 
dataField="parentName" headerText="Parent Name" />
                        <mx:AdvancedDataGridColumn id="removeItemCol" 
dataField="removable" headerText="Remove" />
                </mx:columns>
                
                <mx:rendererProviders>
                <mx:AdvancedDataGridRendererProvider 
                    column="{removeItemCol}"
                    columnSpan="1" 
                    renderer="com.renderer.RemoveItemCheckboxRenderer"/>
            </mx:rendererProviders>
        </mx:AdvancedDataGrid>


And here's my removeGroup() method. It returns null on the 'renderer' variable. 

/** User wants to remove a grouping
                         */
                         private function removeGrouping():void{
                                // Loop over the dataProvider and find the 
items selected, then remove them. 
                                var dpLength:int = 
GroupingGrid.dataProvider.length;
                                for( var i:int=0; i<dpLength; i++ ){
                                        var im:Array = 
GroupingGrid.rendererProviders; // .renderer.generator as 
com.renderer.RemoveItemCheckboxRenderer;
                                        var j:int=0;
                                        while( j<im.length ){
                                                var 
myim:AdvancedDataGridRendererProvider = im[j] as 
AdvancedDataGridRendererProvider;
                                                var 
renderer:RemoveItemCheckboxRenderer = myim.renderer as 
RemoveItemCheckboxRenderer;
                                                j++;
                                        }       
                                }
                         }