[Exim] refusing email for certain local users

After perusing my newly bought Oreilly Exim book (what in the heck is that
thing on the cover anyway??) I have a quick question. My apologies if I
missed something obvious in the reading. I have certain local users that I
never want to accept email for. I want to quietly send these emails to
/dev/null. Is there a facility in the config file to list certain users to
be handled in this way?

Thanks!
CK