Mwan3 script when higher metric if goes up/down but not when cellular goes up and down

I have man3 setup to failover between cellular, wifi, and then ethernet.

If the wifi connection is connected to a captive portal, i dont want its dns interface servers being used even if the interface is up from what dnsmasq can see.
I want to reorder the resolv file based on my logic.

How can i write a mwan3 script that will only run when ethernet goes up as the primary, but not when wifi or cellular go up and down while ethernet is up?

Is there an event for this, or do i need to grep mwan3 status every connected state to determine if a higher priority interface is active?