No changes in the DHCP are needed 99.99% of the time. For that STATIC IP machine, here is an example.

Let's say the network is based on the 10.0.0.x scheme.
Let's say the DHCP numbers start at 10.0.0.10.

Just set that Static IP (on that machine) to 10.0.0.100 and enter in the netmask, DNS and it will just work.

Bob