How to change HUD class whilst playing the game?

I’m trying to make it so that whilst playing the game when you press the right mouse button, the HUD class from the GameMode changes to the FirstPersonHUD and once released reverts back, however though as I tried it out, this transition didn’t actually occur.
I have checked if both HUD classes work and they do, by setting the default HUD class from before I start the game, anyways though, here’s a picture that’ll show you my blueprint:-

What I would try is in your FPCharacter BP, add that right mouse button input, then link it to set ‘aiming’ to true while you hold it and ‘aiming’ to false when you release it. Then in your HUD where you create the widget change the widget instead of your hud maybe?