Need help opening port in back to back isa config

[SysAdmMke]

How do I open port 15425 in a back to back isa config?

ISA 1

Nic 1: Internet Feed

Nic 2: DMZ 192.168.163.1

ISA 2

Nic 1: DMZ 192.168.163.250

Nic 2: Internal


Basicaly I need port 15425 open from ISA 1 and have it point to a machine in the internal network.

I created a protcol on ISA 1 caled PORT15425 and created a access rule to allow External to Internal using protcol PORT15425 but that didn't work.

What am I doing wrong

Thanks
Mike