The 35-year-old "Two and a Half Men" star is taking the dancing lessons with Kunis at his own residence, reported Showbiz spy.
"Ashton and Mila both loved the climactic dance number in the movie. It inspired them to learn fun and easy ballroom dancing. They practise at least four times a week, and they're having a whale of a time. He's even asked their instructor to save it for the end of their session," said a source.
"But he's vowed he will never do Dancing with the Stars. He thinks the show is for has-beens," the source added.