I need to block the Netbios traffic from one specific server from
being routed to our other subnets.  Here's some background:

We have a Windows-based network that spans over 3 locations, each
connected by T1.  We (still) use WINs for some name resolution, so
completely blocking Netbios at the router level is not an option. 
However, we installed a new point-of-sale server at one location and
will be installing identical servers at the other two locations.  It
is important that they not see each others Netbios traffic, though. 
The software is using Netbios to announce it's location for the
point-of-sale lanes to find the server, and we don't want a register
at one location to attach to a server at another location.

We have Cisco routers in between each location.  I tried blocking port
137 (this is the port NCR told us to block) both TCP and UDP but it
either didn't work or I didn't properly use the Cisco access-list to
set it up, or possibly a different port is being used?

What I would like is an explanation of how to configure our Cisco
routers to block the Netbios traffic being generated from this server
but not block all Netbios traffic.

To assist, here are our subnets:
192.168.1.x
192.168.2.x
192.168.3.x

The server that needs to not send Netbios info to other subnets is at:
192.168.2.100

Thanks!!