How to make an texture change based on reloading [TF2]

Hello, I am making a pyro flare gun for tf2 and it has a little screen on it. My partner’s idea it to make it so that when there is a shell loaded in the gun, the screen will display “loaded”, and when the shell is fired, the screen will display “empty”. I tried looking at the .vmt files for the rescue ranger since its the closest i can think of getting it, but the person who made it has a separate .vmt file for the screen itself, which confuses me even more.

I also tried finding the value for when a shell is loaded in the pyro’s flare gun, and just equate that value so that it switches to the next frame once the shell is fired, but I can’t quite tell what the value is and how to make that work.

Any help is greatly appreciated! The screen in context can be seen below. Right now it is empty because I didn’t really bother with it until now.

Unfortunately the only way to do this is by modifying Pyro’s animations and adding bodygroups.

If you want help with that, ask me.