Hi James,
The grouping grid currently has no support for the CELL drag and drop functionality. The work around to handle the TableControlMouseDown event and call the DoDrag method to enable the drag and drop functionality in a cell. The attached sample implements the cell drag and drop functionality and also highlights the cell when the mouse move over it.
Sample :
http://www.syncfusion.com/Support/user/uploads/CellDragDrop_172dfc82.zipLet us know if this serves your need.
Regards,
Haneef