*Allow you to select groups from your contacts for busy messages so that when those contacts calls you they get notified about your busy status and call will be hang up immediately without disturbing you.
*Block specific group calls i.e. Use it as call blocker
*Silent and Vibrate
So its flexible to do what you want.
Try this application as its free with EXTRA Caller ID feature.
INTRODUCING “IMBusy” CALLER ID!
IMBusy caller ID helps you identify numbers real-time while the call is happening - even the ones not in your phonebook. No more number guessing or avoiding unknown callers – IMBusy caller ID prepares you for the call. If your local pizza vendor doesn’t pick up the phone when you’re calling, IMBusy caller ID will suggest alternative nearby places. You can always adjust your caller ID settings in the settings menu.