"I wish that you won't be able to come to orgasm except by having sex with a guy."
"What?! Sarah, you can't do that!" Jon was stopping the masturbation. He was erect, but couldn't get any farther than that.
"But I did!"
"Change me back."
"Tut-tut. You know that wishes can't be reversed." Sarah pretended to think for a moment, but she already had her plan in mind. Then she explained, "But I have a way to help you."
"I don't think you have my best interests in mind."
"Well, that's a matter of opinion. I wish that you'll get a free wish right now, but that you'll use it only to have sex with a guy."
"I still don't have to make that wish," said Jon.
"If you want to be frustrated, I guess you don't," said Sarah. "So I'll fix that. I wish that Jon will make a wish right now that will lead him to have sex with a guy."