Math Functions in Forms

HELP!
I seem to be past the “beginning” phase, since I went through all those forums and boards and didn’t learn anything I hadn’t figured out on my own after using this for a year. But I would not call myself “advanced” by any stretch.
My site is for a school. Students register online. At the end of the process, they get sent to PayPal to pay for it. Last year it was simple, because all of our classes had the same tuition, so we only had one “product.” This year we have a few different classes we’re offering, so different prices, therefore different $ amounts that need to be charged.
The first way I tried to do it is by using the “show this screen if any….” conditional question format. If the customer selected product A, B, or C, they’d be charged X. For product D, E, or F, they’d be charged Y. Sadly, as a lot of you may know, that feature does not work on Word Press correctly. (I remember noticing that last year, when I got my one-day training from our web designer. I was hoping the new version had fixed this glitch, but it appears it’s still not working in 3.3.2, which is the most recent.)
I noticed this fabulous “price” option, where I can assign different labels a price. Great, perfect, just what I need. Now, what does WP DO with that price, and how can I retrieve it at the end of the process, to add it to the other information? I mean, there has to be a way to order multiple products, add taxes, shipping and handling, and have the page do the math, right? HOW????
I need this up and operational by Tuesday. I’ve been working on it for over a week now, and am frazzled to my roots. Any help would be muchly appreciated. Thanks!