allowing applications to access 1 network but not the internet

I have two networks set up on my pc (xp 64) one if for accessing the internet and one is for accessing my render nodes (two xp 64 comps used as servers to render 3d animations). I want to allow my 3d applications access to the render nodes but not to the internet (3d apps are notoriously fragile)

How do I achieve this?

TIA

May be this topic is of inspiration: Firewall: Full Access to LAN, notifications for Internet access?