I feel that a more equivalent challenge would be for a girl to get a man to accompany her to one of her hobbies. That way he has to be interested in something other than sleeping with her. (paraphrased)

I'm reasonably confident I could manage that using nothing but sex as a lure. Given that, I'm not sure how you'd really sort out whether the guy went from genuine interest, or because he genuinely believes there's a good chance of getting laid. If you're meeting someone in a bar and expressing interest, you're dealing with very biasing circumstances.