Look.

He tried to grab my tit, okay? Actually he DID grab me, and he'd been 'accidentally' touching me for weeks and weeks.

So I hexed him so every time he tries to wank his hands turn to rubber. It'll wear off eventually. Or he can go to Madam Pomfrey and ask her to fix it, if he gets impatient. I probably won't cast it a second time. Unless he touches me again.