help with network virus

our network is infected badly, and the worm is spreading thru network for sure. even the freshly formatted pc r getting infected again.
all the clients pc use file sharing on server but do not need to communicate with each other, is it possible to block all communication between clients ?

we did that earlier using arp batch file with fake arp tables and made a list of 192.168.0.2-255, and run thru batch file, but it was tough to run it every time on boot for ever client.