question on DHCPD

[Nick]

I have a user on my network that keeps trying to manually configure access 
to my gateway, for internet access.

Is there anyway to setup the dhcp server to give a bogus alocated gateway.
So far I have used the option to lock down a specific address for the 
client using the MAC address, but how can i do this with out disrupting the 
other machines on the network

I am running potato, with ipchains and dhcp-beta