Erasing parts of a Bitmap?


I’m in need, again, of some assistance. I’m making a game with 2 pictures. and the concept is built on that you erase part of the top-bitmap to see the bitmap under.

How can I accomplish this?

I tried to wrap my head around the bitmaps and the draw and the FillRect but can’t get it to work completely.

Basically I want 2 bitmaps, and a cursor which erases parts of the top one to show the one underneath.