Grant access to one forum section at a time
 

Hello,
I'd like to set up a forum that has top-level sections A, B, C, and D.

When a customer purchases product A, they are granted access to section A in the forum. When a customer purchases only product B, they are granted access to only section B in the forum. If they already own product A and then purchase B, their same username and password now opens up both sections A and B in the forum.

Is this possible with vBulletin?
If not, can anyone suggest either another piece of software that will accomplish this or another way to accomplish the same outcome?

Thanks very much in advance!