I haven't tried this, so I am for certain it will work, but try this:
create a public property in the form
set the property to the location of the form in the init event
on the mouse up event of the form (if there is one, I am a VFP programmer), check the property and make sure it equals the location property of the form.
If not then you know it has moved.

If you can't find a good event to check the property in, try using a timer.
Good luck.