odd way of doing a DMZ

So, I need to set up a DMZ host/network, but I want to do it in a non-standard manner.

The setup is a SXT G-2HnD configured as a router (quickset config right now for a wireless WAN link) with NAT and a DHCP server on the LAN end.

Anyway, I’d like to setup a specific IP address on the wlan side that has been set aside by the upstream router as the DMZ IP address. I then want to route packets with that destination address through NAT to a specific IP address on an entirely separate network).

Any ideas how that might look as supplementary commands in combination with quickset?

I’ve got the secondary IP address on the wlan interface figured out, but the separate network and NAT routing have me confused.

Thanks…