We can access Grid Grouping Control from TableControl by using GridGroupingControl ggc = (grdControl.GroupingControl) as GridGroupingControl
instead of GridGroupingControl ggc = (grdControl.Parent) as GridGroupingControl
.
Here is the code that you need to handle in MouseMove Event:
GridTableControl grdControl = sender as GridTableControl;
GridGroupingControl ggc = (grdControl.GroupingControl) as GridGroupingControl;
I hope the above code will help you achieve your result.