Used a time or two by me:

"If you were enough of a woman to ever find out, you'd be too much of a lady to ask."

A word of warning: while the pretty ones laugh, the ones who aren't seem to take a bit of offense ; )

I used it on Monday night at a local club, and the bartender, overhearing, nearly dropped the drink he was mixing as he laughed. My interrogator wasn't quite as amused....