Hello Scottb,
I am using Vista, but I think I have it working now.
I was going through the thread to review and I downloaded the python script to look over. It turns out I was using the old version.
I haven't had a crack at the math end of things yet, but that part should be a little easier for me.
If you all don't hear from me in the next few days, you can assume I've run aground.
