what do the witches say after macbeth does exactly what they wanted?

The real question here, I think, is what part of the play you are in. When he first hears the witches' prophecies in Act I, he says he has evil thoughts about how to take the throne "that thought that" is beating in his seated ribs. He tries to cast them aside until he finds out that he has become the Thane of Cawdor because of the treachery by the thane. His wife then shames him into killing the king which makes it seem as if he is doing the things the witches wanted. One thing that is clear, however, is that the witches never said "Do this." They simply suggestged what could happen. Macbeth took his own actions based on his own free wil.