With CME there are at least three methods to block calls, two are described in the admin guide and are:

1. login/logout with after-hours blocking.

2. cor list.

The third is that you invent a prefix so that only calls made with it will go through.

Hope this helps, please rate post if it does!

You can use a TCL script for doing that, not natively supported. But you need to contact your local Cisco SE to obtain it. Afaik, this feature has been already incorporated and will be supported in the future CME version 4.3...not available yet.