That's it! So long as Billy Joel was outside of Lake Point, Jon couldn't do anything, but Jon could wish about something within Lake Point that might affect Billy Joel.
Jon reached his hand into his pocket, and whispered so that nobody else could hear, "I wish that Billy Joel owned a house in Lake Point, which he was planning to visit tomorrow."
It was perfect. The house would be within the stone's range, and by making it so that the effect of Billy Joel visiting would be associated with the house, he wasn't even really affecting anything outside of the stone's range. And then tomorrow, he could wish whatever he wanted on Billy Joel in order to fix the girls in town.
Now all Jon had to do was wait.
