You can do this in many ways
1) Use MVA Mobile Voice access. Dial into CCM and use the IVR (h323 GW) or 2 stage dialing (CUCM 6.1 with even MGCP GW) to do toll bypass. This works for internal and external numbers
2) If these users are defined in your VM system as mail boxes then you can do dial by name or extension in the AA. If these are numbers outside of your system then you can define these numbers as contacts since then you don’t take a license. Of course this is cumbersome to manage and maintain and only work if these numbers dialed are pretty much the same
http://www.cisco.com/en/US/docs/voice_ip_comm/connection/7x/administration/guide/7xcucsag115.html
Thanks
Srini