Infinite Variable Additions

I'm currently using the YEP_PictureCommonEvents plugin to make a clickergame. (however this is not a plugin query)

However. I've ran into a problem. For this specfic event, I want there to be an NPC you can battle.

Now in this game to gage enemy health I use variables, so if the player click 10 times on the enemy they win. (This goes in tandem with a parallel process event that ticks down time should the player not click enough in the alotted time)

But for this NPC, for everytime the player wins, i.e when the player defeats this NPC by clicking 10 times, the next time the player challenges them they'll be harder, and you now have to click 20 times.

This is possible with conditional branches and switches, but wondered if there was an easier way to acheive what I wanted where it could theoretically get up to any difficulty, so with the same alotted time you'd end up having to click...100...200 times?

EDIT: Derp, Multiply varibles, sorry mods please delete this im an idiot