Current logged in users in the Win2K dom

Is there any way to find out the users who are currently logged in to a single domain.

My manager wants to know the users who are all currently logged in/not logged in to the network for the past 24 hours.So that he will come to know who ever isworking/not working.
So, is there any way to know that in Win2K OS itself or any 3rd party utility is there?????