forwarders and split dns

[Steve Pfister]

First of all, I apologize if this post appears twice. I posted a question
along these lines to comp.protocols.dns.bind, but I have a rather urgent
need for an answer so I'm asking it again.

We have a sister company with a split dns. They have an external server for
their public name records, and an internal server, which among other thing
gets dynamically updated by MS Active Directory.

We need to be able to query the external server for most records, but still
be able to forward to the internal server queries for the AD records (which
aren't in the external dns).

Can we set our server up to query normally, and then forward to the internal
server (which we have unrestricted access to over a point-to-point T1) when
the first query doesn't return the required answer.

I know there's a 'foward first' directive. Is there any way to make a
'forward last'?

Thanks!

--STeve