subnet and routing

Hi all,

I am using to separate the 192.168.3.x subnet from our main 192.168.2.x
network to isolate it.
I managed to route everything from inside the 3.x subnet to 2.x and to the
external internet via our gateway 2.1.

The m0n0wall WAN IP addr is fixed to 192.168.2.10.
Now I need to allow special machines to access a host on 3.x from 2.x. How
do I do that?
Is there a way to allow a transparent routing for this machines? What would
be the correct NAT to use?
I would like to access the machine 192.168.3.10 and 192.168.3.11 from a
machine ie. 2.55.
How can i achieve this?

Thanks,
Alf