I think there’s no Natural environment variable containting the IP-Address. You can use *HOSTNAME instead. But I’m not sure if this would really help you.
If I understand you correctly you want to assign printing jobs to a printer by using an IP-Address of the user, who created the print job. Are we really talking about terminals? From my point of view, all programs started by terminals are running on one host. So all your jobs would have the same IP-Address. If possible, I would take *USER or *USER-NAME as an ID.