user management

user management

Currently I can only add and delete users, and assign a role. It doesn't seem to me that the roles really make all that much difference regarding access rights. I am interested in being able to restrict users from certain aspects of the project site. For example I would like User A to see the tasks, calendar, and documents, but not have access to the forums or I would like User B to have access to the documents, but nothing else. I realize the point of a project site is full collaboration of all members, but some of my group need limited access. How can I do this within the current user administration structure?