Years and years ago, I remember some story where the curse worked this way, but I have no idea what story it was. Possibly an episode of the old Suspense radio series...
06/04/25 edit: More than 10 years later, I learned that the story I'm stealing this gimmick from is "The Bottle Imp" by Robert Louis Stevenson. Webcomics are so educational!
Seventy-Three - Fits and Starts