If I understand your concept, you are trying to make one of those devices that has 5 or so steel balls each suspended on a triangular frame supported by a open rectangular frame, yes? If so, you are not really dealing with motion paths at all. Form a group of the first ball and it's support. You will need to turn on the origin handle for that group. Then shift the origin handle vertically until it aligns with the pivot point of the support. Then all you do is rotate the group and it will rotate about that pivot point. Make keyframes for the movement and do the same for the ball/support at the opposite end. I threw together a quick object for you to visualize what I am talking about. Download it here: http://www.wolfiesden.com/cgi-bin/downlist/browse.dl.cgi?Ball_Support.zip