virtual disconnect from network

Is there a way to virtually disconnect your system from a network? 10/100baseT, Ethernet, Windows NT 4.0 SP 4 server with a nasty assistant LAN administrator who keeps using me as a test dummy to assimilate through a series of pounding scripts using KixStart. I want to be able to log on to the network, run a program to simulate yanking the cable from the NIC and plug it back in when I have to do network stuff, in other words minimize his time to rake control over my machine(he actually checks to see if the cable is attached!). I think a network should be helpfull and not a hinderence! Any ideas?