Emulating RBAC using FIM Service and Portal

Hi!

I am trying to create a simple RBAC using standard objects of FIM Service. So i am associating type "Set" with role, expanding it with multivalue reference attribute "ListOfPermissions". I want to achieve the next behavior: when user dynamically join to the set the MPR is executing custom workflow that adds this user to the members of according permission object. Rather simple, BUT is there a way not to specify MPR for every set manualy, but specify it ones with next logic for example: when someone join to any set with IsRole flag set to 1 the MPR is executed and etc... as described above? The straight-line methods have not yielded results.

Need any help, thanks in advance!