Isa Server, how to configure for allowing use of RAdmin

I normally set up Radmin (remote administrator) to go to a particular
computer by defining NAT (ie external IP say 100.100.100.100 and port 4899
goes to internal address on remote network of 192.168.1.15. That would be
defined on the remote Linksys router.

This is easy on routers like Linksys, but how do you do it in ISA server
when you have two networks each with its own ISA server? I Think I need to
allow inbound and outbound traffic on that port on ISA server1 (my local
one) and also allow inbound and outbound traffic on that port on ISA
server2 - The remote server. How do you do specific NAT translation on isa
server for a specific port like described above?

For now we did not set up a vpn between the two networks and don't want to
do this for now.

Thanks for any help,

Bob