How do I make a loop in my procedure go on forever until something stops it

Context: I'm remaking my Dune mod and I made the spice refiner;

what I want is that in the GUI, I press the button and it works works through all the fuel or spice sand, and then it stops until I put in more fuel or more spice sand and press start.

Procedure context: the FuelTimer Variable, is basically how many spice is made before it uses one coal or charcoal