Please help with after effects (ongoing)

[Bobtheduck]

Ok, as I explore this imensely powerfull, I'm guessing, but immensely difficult to understand product, could I get help from some current users on features here? I'm on Windows XP using AE 7.0 that comes with Production Studio (the latest one, as of 11/17/2006 with Premiere Pro 2.0, encore 2.0, Photoshop CS2, Illustrator CS2, Audition somethingrather.0, but NOT the set with flash)

With that out of the way, I'm trying to do something very simple. For practice, I thought I'd try something I saw on red vs blue, and have text move behind something (also on the transporter opening, and a number of movies in credits) I build a text layer, then draw the mask with the pen tool, set it to "subtraction" and animate my text, except... It animates the stupid mask with it! I can't have the text move behind the mask if moving the text moves the mask, so how do I remedy this?

As a comment, Levels would be so much more usefull in premiere/after effects if it had black, white, and grey eyedroppers like photoshop. I have some iffy video I'd love to try to spruce up a bit with levels... Trying to do that manually isn't quite the same for me...