Best Approach for defining User Access Levels

Hi. I've set up a membership site that has different levels of users. Each member's DB record has a "user_status" field that has a number from 1-9, 9 being the highest (Admin) level of access. This has worked okay, but, I'm finding this system of granting access too limiting, and need finer control over who has access to what. Does anyone know of a better system for granting access to groups of users that isn't too complicated but is flexible enough to add or remove access to whole groups of users? I'm trying to not reinvent the wheel here if possible. Thanks for any suggestions! Monty