Log Change of a Users Group membership

Have 10.5.8 Leopard on XServe, and have 25 users. All are members of ‘staff'(primary) group as well as other created groups, like, compmgmt group, compusers group, etc.
I would like to know where or how do i go about getting a log of an event when a user is added to another group. Or when a newly created user is added to the compmgmt group, can I view that event in Console as a logged event?
When I add a new user or change a users password, I can see the event logged in ApplePasswordServer.Server.log
But when I add a new group membership to the user, I can’t find the event logged anywhere in Console.

Appreciate you help in advance.