I know it sounds weird, but is it possible! I've only managed to change the volumen of but not completely mute them.
I read an article once where Angus Young said he taped strings down so he didn't get buzz from the other strings. I think he did that when they recorded Thunderstruck, of course, he was muting the strings around the B string though. Not Sure if that's what you are wanting to do. If you are trying to just mute them for one section of a song while playing live, that wouldn't work.