Problem while creating my own user groups.

Hi, In my xwiki application we have got a hierarchy of users, viz., admin(xwikiadmin), monitors, registered users, banned users, and guests(xwikiguest). In our application admin can create monitors. Monitors are users having some special rights. Monitors can assign rights to a set of users viz., the registered users (who doesn't have admin rights). Monitors can ban a registered user etc. But to allow this monitor should have admin privileges (see - http://www.xwiki.org/xwiki/bin/view/UserGuide/RightsManagement). But if we give admin privileges to monitors, then a monitor can even change the rights of an administrator, or even his own rights. Is there a way in xwiki for me to do make a user group so that he is not able change the rights of admin but is able to change the rights of normal users? Another query : how can I get the group of the currently logged in user from a velocity page? Regards Roopesh