Hershel,
You would handle this with changing the description of the users DID to say Private, No CID, Blocked, or whatever makes sense to the user. We do this a lot with the description of a CO Trunk Group for POTS lines or T-1 channels for when a call comes in without caller ID information so we don't post the 92xxx of the trunk group that the call comes through. Keep in mind you only have a few characters to work with though at the CO Trunk Group level as opposed to the Call Routing level.
Thanks,
TE