Multiple Access levels Overlap?

Hi,

I'm using your Membership plugin and I'm thinking it's overlapping with other access levels.

Here's the idea.
Since we have 5 exams to be taken and paid individually, we have 6 access levels. One to all the site (except the exams), and the rest (being the exams) block the exams which aren't themselves.

Example.
level exam 1, blocks exam 2 - 5
whilst level exam 2, blocks 1,3,4,5.
Got it?

I have it with positive rules on the first level (being the whole site except exams), and the exams are all in negatives only as I mentioned earlier.

I tried it having one user on the exam 1, and it worked for a moment. Now I can't get it to work again. Also, not sure if having access to "exam 1, and exam 3" will overlap, as one blocks another :s

Is there an easier solution to this?
thanks in advance.