If you are just part of a hunt group, you could log out, then foward your phone.
If you're part of an extension list, you'd have to program it to work as above.
You could alway try the first step and test it, if it doesn't work, you'll probably need to have someone program this for you unless you're familiar with the system.
I beleive 324 is the feature code that will log you in/out of hunt groups.

Let us know if that works.

Devin