Dual Function Call Subsystem Implementation

I am working with a real-time Simulink application and have two network interrupts that trigger IRQ Function Calls. I have a function call subsystem that needs to be triggered by either function call source depending on which is active (state of a tag say "network1Enbl")

So if network1Enbl = 1 use Function Call 1 to trigger the subsystem, else use Function Call 2.

The issue is obviously that you cannot preform normal operations on the function call signal or take in two function calls to a single subsystem.

My question is how can I implement this functionality, would it be possible to implement a custom S-Function to take in both Function calls and the network state, then output the selected Function Call? Perhaps there is there a more straight forward way to do this?

Would greatly appreciate some guidance, Thank you very much.