feature not available

Hi,

This is going to sound like a newbie question but, is there a way to make 
a DNS server use forwarders iff it doesn't have the entry in its local db?

i.e.

domain.com is hosted internally and on the Internet. (I know bad practice, 
but I inherited this setup)

If host1.domain.com doesn't resolve internally, is there a way for the DNS 
server to send the request for host1.domain.com to its forwarders (which 
can resolve host1.domain.com on the Internet side)?

Kinda like an nsswitch.conf

hosts: files dns

??

I can't seem to find anything that would be able to do this.

Thanks,

Don