             return chb.dataGrid.grid;
         
         return null;
-    }       
+    }
+    
+    //----------------------------------
+    //  overlayGroup
+    //----------------------------------
+ 
+    private var _overlayGroup:Group = null;
+    
+    /**
+     *  @private
+     *  The container for columnSeparator visual elements.  By default it's an 
+     *  element of the GridColumnHeaderGroup's overlay.
+     */
+    private function get overlayGroup():Group
+    {
+        if (!_overlayGroup)
+        {
+            _overlayGroup = new Group();
+            _overlayGroup.layout = new LayoutBase(); // no layout
+            target.overlay.addDisplayObject(overlayGroup);            
+        }
+            
+        return _overlayGroup;
+    }
 }
 }
    
    //---------------------------------------------------------------
    //
    //  Internal methods
    //
    //---------------------------------------------------------------    
    

        
        const columnLeft:Number = grid.getCellX(0, columnIndex);
        const columnRight:Number = columnLeft + grid.getColumnWidth(columnIndex);
        const smw:Number = columnHeaderGroup.getStyle("separatorAffordance");
        
        if (!isFirstColumn && (x > (columnLeft - smw)) && (x < (columnLeft + smw)))
            return grid.getPreviousVisibleColumnIndex(columnIndex);
