Overlapping Images

I need to overlap to PictureBoxes into another one. I mean, I have three PictureBoxes (the two source is an array, actually) and the TargetPictureBox. In both SourcePictureBox I have a similar picture (with the same background) but different foreground.
I want to overlap the two sources images to have the overlapped picture in the TargetPicture. Besides, I want one of them to be moved 15 twips in X, and 15 twips in Y.
Am I clear?? I'm kinda trying to achieve a "shadow". Can anybody help me??

Well you could always do a loop through the x and y pixels of the pictureboxes, and then average the colours of both, and then use pset to stick that colour onto the third picturebox.

I dont know if that will create the effect you're looking for ...

I don't know if that would work... but it doesn't sound to be that fast.