Modem and VPN

Hi,
I have a Modem hooked up to nt 4.0 computer (server).. Is there any way to tell when someone has dialed in and also what they are doing and where they are going on the network.
I also have a vpn setup and I can tell at what time the users are on and off the system through the event log. But is there anyway to tell also where and what they are doing on the network..
Any help would be appreciated….