Split DNS Forward problem

[Diederick van Dijk]

Our company have been taken over by a larger company. Now I've to configure 
our DNS that it resolvs the domain names from the company that has taken us 
over. Problem is that they are using a split DNS system.
So I can make for example a forward zone in my DNS and point that to the 
internal nameserver.But then the external hostnames aren't resolvable.
Does anyone know a solution ? I'm using Bind 9.3.0. 
Altering the split DNS system is a nogo.