source and destination nat in one command

Sophos can do following.

src_address-any  destination_address-public_ip1 service-port 6880

Change source to - public_ip2

Change destination to - public-ip in internet

public_ip1 and 2 are in same subnet on the firewall.

So traffic comes in on port and is redirected to go out to a public ip in untrust.

How can I achieve this with ssg5.