Not natively in CM.
However, there is an *unsupported* sample jsp application in the SDK called autodialer that can do this.
From the app description:
// AutoDialer is a simple example of how a custom phone service can be used to dial numbers which require
// pauses in the dialing sequence - long distance services, calling cards, voicemail access, etc.
// When the user subscribes to the AutoDialer Phone Service, they will be required to enter a dial string.
// When the user invokes the AutoDialer service from their phone, their specified dial string will be dialed.
This would need to be installed on a web server (not on CM)
To locate the IP Phone Services SDK:
http://www.cisco.com/go/developersupport
>supported products
>log in now
>VOICE TECHNOLOGY/AVVID
>(pull down) CallManager IP Phone Services SDK
thx,
Neal