newly
the pixel 
is 

You could set up a bitmap with a mask in it.  Clear the
bitmap, draw the rectangle to be deleted with GXor.  Draw the one
that is to stay with GXclear.  Then GXxor the entire pixmap with
the screen.  

Note that this is a pretty effective way of animation, if you ever
need to do that (replace the GXclear with a GXxor).

----------
Joe Hildebrand
hildjj@fuentez.com
Software Engineer
Fuentez Systems Concepts
(703)273-1447