Here's what I'm trying to do...
Three lists:
A = Prospects
B = Buyers
c = Multiple-time buyers
When someone makes a purchase, they opt-in to List B. They may or may not be on List A already. If they are on A, I want them removed when they confirm for B.
When someone buys a second time, they again opt-in to B. I want them automatically add to C instead.
How would I go about this in an efficient manner? I'm learning some php and MySQL, but right now I know just enough to be dangerous...