Another Pop-Up Window Question

Like many people here, I’ve tried the perfectly centered pop-up window tutorial and I’ve had good results. The only problem however is that I’m not looking to center my window in the middle of the screen. I’m sure it’s embarassingly simple to do, but how do I control where the window appears on the screen? I want to be able to move it to the left, right, top, or bottom with a fair degree of control.

I’ve tried looking through several of the other pop-up window threads on the forums without finding the answer, but if anyone can point me to a thread that touches on this, or just help me out here, I’d greatly appreciate it.