Unfortunately the only thing Ive found was this 14 day trial thing.
No Calls is a Windows Mobile® application that can automatically reject incoming calls depending on the caller. It silences your phone within the first ring. The caller will reach your voicemail, and you will still see their missed call in Call History. It's perfect when you're working, relaxing, sleeping or out on a date. With
No Calls, you can avoid unwanted calls, yet keep your phone on for the people you care about.
from
http://www.trinketsoftware.com/NoCalls/