Yes, you will need to add an ipchain rule. At a terminal prompt, input:
ipchains -A output -j DENY -p tcp -s 0.0.0.0/0 -d x.x.x.x/32 p
where:
x.x.x.x = ip address of machine you want to protect
p = port
Nice thing about ipchains is that if you make a mistake and are unsure how to fix it, reboot your machine. This clears all rules input at the command prompt.
Greg