Products with Expansion Packs

I have a hunch that the answer to this question is that I have to design a custom "member.php" page, but just in case it's NOT the answer, I'll give you my situation.

Let's say I have two main products, Product A and Product B, and the way my system is set up you buy one or the other - you can't buy both.
A and B are both free, but you can buy subscriptions with more features for additional fees.

So my product roster looks like this:

A
A1
A2
B
B1
B2

Here's what I want to do. If you get A, you can't get B, B1 or B2. You also can't get a 2nd A. But since you have A, you CAN get A1 or A2. Same for B - once you get B, the only thing you can get is B1 or B2. And you can't get B1 or B2 unless you already have B.

Is a custom-built version of member.php in my future, or is there a way to do this in the Product Setup or some other screen that I'm just not seeing?

If I have to build a custom version of members.php, that's fine, cuz I'm not really thrilled with that as the landing page for my Members Area anyway.

Thanks
--Neil

Yikes...

I just looked up the code you referred to; editing that is so far over my head it's not even funny.

Thanks for the answer anyway. I'm not quite sure where to go from here.

--N