Automatic rerun of xmodmap when global keyboard layout changes?

I want my system (each of my fedora/debian VMs) to automatically run

xmodmap -e "keycode 14 = 5 U203D 5 UD203D"

to make Shift-5 type the unicode character “‽” instead of the usual “%”, regardless of keyboard layout.

I.e. this should happen on launch and every single time the global Qubes changes the keyboard layout. How to achieve this?