Print unused TN's w/your type as 500. if you have phantom TN's, you'll see them towards the end of the list. they usually have higher number Loops, like 64 or 120. they'll also say PHTM or PHNTM, something like that.
from LD 10, 11 or 20, build new, enter 500 as the set, then the Phantom TN. add your DN, fill out the other prompts, then when you get to the FTR prompt, enter DCFW 4 DN.
basically you're telling the Switch to Direct Call Forward to 4 digits and you're giving the extension you want calls forwarded to. good luck.