Shutdown Machine When Virus Discovered

Hi,

I am running a small internal network 2K3Svr/XP Pro with McAfee VS 8.5/ePO
3.6. I have some users who keep introducing virus's from extenal media -
usually flash drives - and I want to "educate" them to use the sheep-dip.
What I want to do is lock out their machine automatically as soon as a virus
is detected, so they can't use it until an administrator attends.
Can anybody suggest a way of doing this?

Many thanks.

Adrian