asterisk users - Jun 2005 - Automatically setting mailbox on registration of SIP device by SIP device's line #

Hello,
Is there any way to have a SIP device get it's mailbox automatically set 
upon registration when it does not have an entry in sip.conf? I would 
prefer to not define all my 200+ devices in my sip.conf's. All my CID is 
set via an AGI from database or ldap. All I need it to do is set 
mailbox=sip_line_#. If there is a patch in progress for this, I'd love 
to test it out.

Thanks in advance.
-Jonathan