Creating a DHCP reservation to the specific MAC addresses is one option, however, can write a plug-in, called a Callout DLL, that the DHCP Server can load.

This plug-in can be used to affect the processing of DHCP packets at various stages. One of the actions you can take is to tell the DHCP Server to drop the packet.

For details on using this API go to: http://msdn2.microsoft.com/en-us/library/aa363372.aspx