You are PROBABLY looking for the DragOVER() method instead of mouse move. However, you need to identify if the "source" control is in "Drag" mode or not (based on manual vs automatic use of drag/drop). When a user is finished dragging an item and lets go, the DragDrop() method is invoked of the control you are dropping ON, NOT the dragdrop of the original control you started the drag operation.

HTH