Decrease variable after pressing a button

Questions & Answers
1

I was wondering how I would go about setting up a variable in my code that whenever I interacted with a certain game object the number for that variable would go down. So far, I have code that allows the player to interact with the object in the first place after pressing a button.

void Update() {
		if (Input.GetButtonDown ("Interact") && currentInterObj) {
			if (currentInterObjScript.npc) {
				currentInterObj.SendMessage ("TriggerDialogue");
			}
			if (currentInterObjScript.interactable) {
				currentInterObj.SendMessage ("GoToClass");
			}
			if (currentInterObjScript.inventory) {
				inventory.AddItem (currentInterObj);
				currentInterObj.SendMessage ("DoInteraction");
			}
		}
		if (Input.GetButtonDown ("Continue") && currentInterObj) {
			if (currentInterObjScript.npc) {
				currentInterObj.SendMessage ("ContinueDialogue");
			}
		}
	}
2

int VariableToGoDown = 100;

void Update() {
         if (Input.GetButtonDown ("Interact") && currentInterObj) {                 
             VariableToGoDown--;
             //Do whatever you want to do else...
         }
         if (Input.GetButtonDown ("Continue") && currentInterObj) {
             if (currentInterObjScript.npc) {
                 currentInterObj.SendMessage ("ContinueDialogue");
             }
         }
     }