Looking for multi-customer DNS system for an ISP

[CHANGE username to westes]

I'm looking for a web-driven application that would let customers of an ISP
configure and manage all domains that they own.   The configuration
information, once written, would then be fed to either bind, or to some
custom software that can act as a DNS server for multiple, independently
configured domains.

Does such code exist either in the public domain, or as a commercial
product.   If some vendor has implemented such an idea as a consulting
project and has rights to the code I might be interested in purchasing it.
Any references to existing implementations are appreciated.

--
Will

NOTE:   To reply, CHANGE the username to westes AT uscsw.com