Hi Marjan,
This will be pretty simple once you get the hang of it. The “problem” is using the Levels make things confusing because S2Members creates levels to be cumulatives, but if you don’t want them cumulative, you should use ccaps – Custom Capabilities (even if you call them LEVELS).
Let’s say you have content A, B, C, D, E, F
Content A and B is for anyone who has LEVEL1 ccap
Content C and D is for anyone who has LEVEL2 ccap
Content E and F is for anyone who has LEVEL3 ccap
So you will protect Content A within these shortcodes:
[s2If current_user_is(s2member_level1)]
Content A or B and will be accessible only to Members with LEVEL1 ccap.
[/s2If]
[s2If current_user_is(s2member_level2)]
Content C or D and will be accessible only to Members with LEVEL2 ccap.
[/s2If]
Now, since a member cannot be at more than one level, that is why you will include the LEVEL as a ccap instead. So in your Paypal button, you will have LEVEL1 or LEVEL2 or LEVEL3 included. If you want a member to purchase the content to more than one level, then you include all of them like LEVEL1,LEVEL2,LEVEL3 in the ccap.
So what you call LEVEL4, does not need to have its own ccap since LEVEL4 = LEVEL1+LEVEL2+LEVEL3 so since the member will get all those levels in their ccaps, they will be able to access the content you protected with the shortcodes.
Does that seem clearer?