preventing object overlap

[Byron Turner]

I have images that the user can drag around a grid and I want to make 
sure that they don't overlap (one dragged on top of another).  I've 
tried trapping for mouse messages (mouseenter, mousewithin) but they 
seem to not function while the mouse is down.  Drag enter seems to only 
work if something is being copied, not just moved around.  Any 
thoughts.

Byron

"Naturally the common people don't want war . . , the people can always 
be brought to the bidding of the leaders. That is easy. All you have to 
do is to tell them they are being attacked, and denounce the pacifists 
for lack of patriotism and exposing the country to danger. It works the 
same in any country."

--Reichsmarschall, Hermann Goering