With MCM you should use GKAPI along with an external apps, which would do it. As far as I know there is only one apps called Click to Meet that supports Cisco's GKAPI where you can manipulate the digits. The GKAPI is available, so if you have programming skills, write a simple apps yourself.
Not so long ago in one of the previous posts a Cisco engineer was saying that there is a plan to put this feature in MCM cli.