How do I route outgoing traffic back inside the network to an internal IP? Using Free BSD...

I have an external IP address that I have assigned as an alias to a nic card on the firewall.  I also have a rule in the pf.conf file that forwards all traffic coming in on the alias to the correct internal machine.  The issue is that internally, if the device requests the external IP, it is not routed back to the internal machine.

I think I remember hearing that there is an issue with going from inside the network to an outside address and beck inside again???

Anyway, I just need a way to tell the firewall that any internal traffic outbound to a specific address, should be sent back in to another internal IP.

Does this make sense?  I hope so.

Please help :)

Thanks.