variables are real easy... But I don't have XP anymore... So I can't help you through it...
I guess, though, it's easy in the way that math is easy.
That is, when you don't understand it, it seems so daunting, but when you learn how it works, you look back and say, "a DOY! How did I not understand that???"
The point is, just try looking through the variable options a few more times. I think that if you do, you will figure it out before too long.