Thanks CoolClark, I have had a go, but no success yet. I'm not sure if I have communicated my problem well - it is clients trying to get in from outside that I need to give access to. I have remote sites that need to come in through the permenant internet connection on the SBS server, that need to see the special port that is currently available on the internal network. So it looks like this:
SBS server FileShare server
WAN NIC LAN NIC NIC
210.13.213.38 192.168.0.110 192.168.0.111
On internal network can see port 23053 on 192.168.0.111.
External clients need to see 23053 on 210.13.213.38.
If NAT can do this, what do I set as the public port number when setting up the special port?
I had another tech say to me that I should be doing all this under Publishing in ISA server - is that off the track?
Thanks again for the help.