Securing 2 computers in LAN

One of my clients has following setup:

A wired corporate LAN (192.168.0.x) with about 50 computers, 30 of which are in a domain & the rest are in various workgroups (they are to be migrated to domain as & when the time permits). A Samba server acts as a domain server.

He also has a router which only he & his secretary share, the WAN port of the router being connected to corporate LAN & 2 computers connected to LAN ports of the router (192.168.2.x). This was done for security reasons as there are some files on these computers which have to be accessed only by these 2 people.

Now the problem is that they cannot join domain as NetBIOS does not work across router. Could they be joined to domain by connecting them onto the corporate LAN & some VPN tunnel between these 2 computers so that the data on these 2 computers is not compromised & nobody else can access these 2 computers ?

 

Sounds like a pretty complicated approach to a relatively simple situation but I don't pretend to know anything about Samba. About the only help this is author can provide is to advise you would probably have better success re: getting an answer if you got someone to move this over to the networking forum.