Different connection for incoming and outgoing?

In any of the units that have a Modem, is it possible to arrange for one connection to be used for connections originating from within the network, and a different connection for incoming?

For instance, I have a static IP use with the modem for incoming connections to devices inside the network, but I want to use the WiFi for outgoing traffic as the static IP is metered. If I have a wifi connection to the router, and a modem connection, it will always use the WiFi, and incoming connections are rejected until it ‘fails over’ to the modem, at which time the incoming connections work but all traffic is now on the modem. It seems to be an either / or.

Is this something that can be done, and if so, how?

Thanks!!

Unfortunately you cannot do this.

That’s a bummer but thank you.