can I configure Nat rule to pass certain traffic to a failover wan interface

[adam3914]

I have a failover wan group with my isp modem and a cellular modem.  My cellular modem is plugged into OPT1.  The cellular modem has an IP address of 192.168.5.1.  I would like to be able to access its configuration page even when it is not in use.  I tried to do this with an outbound Nat rule on the OPT1 interface.  Is this even possible since the default state is to use the normal wan interface?