First, right now I'm using a button in combination of a piston and a redstone block to pulse a circuit that will dispense an item out of a dispenser. I was trying to come up with a solution to instead of a button, use a lever to pulsate the piston whenever the circuit ends, but I couldn't figure that out, So I used a button instead. But now, the circuit just keeps going and going and going, so I would like to only be able to activate this if a level is turned on. Basically if the lever is off, no matter how many times I push the button, I don't want anything to happen, but if the lever is on, pushing the button will start the circuit loop, then I don't want to be able to push the button again as it will just create a second pulse and dispense the items too often. I would prefer an option that omits the button and I can just use a lever (it will make the whole system more simpler). I attached an image of my current build.
The button is on the single iron block on the right, and as you can see, the redstone bridges over the other redstone coming from the button, so there's no possible mis-functionality with the circuit, then it goes into the piston and sends another pulse, and repeat. I would love to use a lever instead. Is this possible?