Well, not easily. You can exclude ranges by restricting the first digit (i.e. so you can prevent outside callers in a handler from dialing anyting starting with a "3") - but you can enter a list of extensions they can dial and exclude the rest.
If you can't arrange your dial plan to accomodate that, and you have a fairly finite list of extensions (i.e. under 100 here) you can go a little wild and chain call handlers together to get the effect - but it's a little leg work.
One the top handler you'd lock and ignore all keys except 3 (and probably * so they can sign in if they're a subscriber) - 3 is locked and set to go to a 2nd handler which has the same setup - the 3 on THAT handler goes to another which then will accept all digits from 0 to 9 which goes to the final level of your tree which has hard coded "attempt transfer for" links to the target subscriber boxes.
Short story you'd need 2+10+99 = 111 call handlers total to pull this off. It sounds daunting but with a tool like Audio Text Manager is actually goes pretty quickly. Not sure if you're wanting to carve off that kind of effort for this, however.
