Run some code like this:
WHILE 1 TOUCH OUT T,X,Y ?X,Y WENDtouch the screen on the edge, and try pressing on the other edge. The detected position will changed based on the pressure. If you press both positions with the same pressure, it will think your are touching in the middle of the 2 points. However, it you press twice as hard in one spot, it will detect the touch closer to that point than the other.