FormCalc Scripting

I apologise for this very basic post, but I'm going nuts trying to make some sense of the FormCalc scripting. I have had Designer 7.0 for over a year, but just now have decided to try it. I'm very pleased with the results so far, but I have run into a HUGE wall. I have no previous experience with scripting of any kind so I'm now stuck in the mud with trying to finish my form. I did manage to create a script that would add my subtotals in the total box, but I'm having another problem.

Is there a way to designate a specific price when one chooses a specific item from a drop box, or if easier, a radio button? Even more important, instead of just giving me a script, I would love to try to work this out on my own first but I have no idea how to go about it because I have no understanding of the functions that are listed in the function box.

I've tried for 4 days searching the web to find an easy to follow tut or reference to help me, but have failed. If anyone can point me in the right direction so I can get started, I would be eternally grateful.

Stewie