Capture which IVR option was pressed

I don’t recall where I was reading but I remember reading there was a way to log which option in an IVR was pressed. I have options 0 and 1 going to the same destination and I need to split it and have 0 go somewhere else. I have a theory that more calls than I think are going through option 0 and I want to be able to prove the theory. I have done some googling and looking here in the forum but without luck. So either my memory is bad or I am not searching for the right keywords. Can anyone out there throw me a bone?