an audit system like you are talking about is really just inserting a record to a database whenever the user performs an insert, update or delete.
create a table to record the information.
on the insert update and delete pages, add an insert record behavior that will store the IP, and other info you would like to track. On the insert page, set the column that tracks the action to ADD, on the update page, set the tracking column to update etc...
in the archived documentation section of the security assist support page, there is a tutorial of user level authentication.