I think that would require something like this:
Portforwarding/NAT on 192.168.45.254:xx --> Object(192.168.45.45 translated to 192.168.1.45):xx
Where xx is the portnumber.
I don't believe thats possible yet, you can only create objects with Name and FQDN/IP-address as I've seen so far and not any object-NAT.
/CK