[SOLVED(in fact never should have been asked)]active mapping

Now, I know a bit about picture mapping, HTML, PHP and javascript. What I want to do is, enable a user to click four different points to create a rectangular mapping area (should I have posted it in the PHP forum?If so please can someone remove it. I really don't know where to ask what). But I have no ideas about how to do so. Perhaps assigning the coordinates where he clicked to four different variables? Can somebody please help?

Oh forget it. I think I'll just do a VB application to determine to points. Thanks anyway to everybody who read this thread.