I don't know why the Z-Order doesn't work. After all, I'm paint lines over a picturebox. What you could try is to add a picturebox (with borderstyle set to none) and set this picture zorder.

About the copyright, I mean if you used the code to write your own OCX. I would like to get the credit for the original idea, or the code (you might get improved). But if you want to give me the credits anyway, I won't turn you down.