Yes, you can do this - you need to setup a call handler to transfer to the number you want, including the trunk access codes necessary for such a call. It's a good idea to use the alternate transfer rule on the call handler to be sure it's always active and to use a release transfer when dialing an outside number since call progress to do supervised transfers can be tricky here.
On the user input for the subscriber in question, map the "1" key or whatever to "ring phone for" the call handler you created.
More details and lots of other information about things you can do with audiotext applications can be found in the audiotext applications document here:
http://www.ciscounitytools.com/Documents.htm
