Thanks JohnPoole...
I ruled out Hot Dial because I didn't think a feature key could be used on key 0. (Stupid, stupid! Never assume!

) So after ruling out the offer of manipulating the tables (I assume this would affect the whole system?), I tried programming key 0 as a hot d key.
I did have a couple of back-lines on the phone, with the LPK set to 4, and found that if I didn't change the LPK to 0, when I picked up the handset it would skip over key 0 and grab dial tone from the SCR on key 1.
So I changed the LPK to 0, and this forced it to pick up key 0 and dial 9.
I hate requests like this - how hard is it to just press 9?
Now I have to deal with caller id issues - the phone company was only sending NPA-NXX, expecting the remaining 4 digits from my PBX. With no DN defined on the key, callers only see the NPA-NXX.
Anyway, the initial request appears to be feasible... thanks for the tip!