[BlueOnyx:01277] How do I change the port for a vsite?

[Support]

Hello,

I have a vsite sitting on my intranet NIC (ETH1) but I need to move it from
port 80 to another port.

I have ETH0 (192.168.10.x) pointed to our VPN and ETH1 sitting on the local
network (192.168.0.x) with the internet connection coming from our
192.168.0.1 router.

The BQ box is effectively fronting our VPN (which does not use the normal
internet connection - it has its own external connection) and I want to be
able to forward port xx from the internet connection to ETH1 on the BQ box
but there is an existing forward for port 80 to an SBS machine.

I tried a few things and could not make it work so I am obviously missing
something important. I am very much a Linux newbie so any help would be
appreciated.

Thanks

Tony