UCD stands for Uniform Call Distribution and that's a whole nother topic but is basically your "ACD" system or at least the backend on the 2000ips that enables your ACD system.
Moving on...R4+Z is right, it get's complicated from here and without knowing what ACD product you are using, it's impossible to help.
My suggestion, build a new virtual in CM 11 on an unused vlen. Starting fresh is a good thing. i.e. 11>199>199 assigns 199 to vlen port 199.
Set your call forwarding via E6XX commands, i.e. E600>199>125 where 199 is your new virtual and 125 is the destination station.
Then, simply point your DID route for the propper mode to the new virtual - for you outside calls.
i.e.
7600>5555>199 sets DID 5555 to route 199
7601>199>199 sets route 199 to ext 199
7602>199>500 sets route 199 to 500 (like 500 was VM for night mode)
7602>...for A mode if used
7603>...for B mode if used
Test time.
Good luck!
-Phil
@tell-a-tek-dot-com
@the-comtel-group-dot-com