Hi Ted, Welcome back. We've sure missed you over the summer. I hope your travels were pleasant and restfull. I really appreciated what you are doing here and I find your instruction well thought out and very easy to understand. As a minor note, you might want to correct the "Opacity_map.jpg" link above to read "Opacity_map.zip". It's a minor thing, but I suspect you're the kind of guy who would want that corrected. Regards, Lou