DNS config help

[AN]

I have a question about how to configure DNS.  My local network is 10.x, 
and I sometimes need to connect to a remote VPN.  My question is how do I 
configure BIND to forward queries to a different server only for a 
specific domain.

When I am connected to the VPN, vpn.example.com, I want queries for 
anything going to example.com  to go a specific DNS, and everything else 
on 10.x to go to my regular DNS.  Please let me know if I need to provide 
more info.  Thanks in advance for any help.