Check out MouseDrag() and MouseDrop(). I find that it's easier to trap when a drag action actually begins and then handle the entire lifecycle of the mouse drag event over the lifetime of a single sleeping proc, rather than spreading it across a bunch of mouse proc calls. You really don't want much behavior in MouseDrag(), because if you have MouseMove() defined in your project, it can be called more than once per frame. It's much better to only update draggable objects' position a single time per frame if you are going to actually handle them with on-screen objects.