Is this your machine?
http://www.amazon.com/9960-600-Stitc...dp/B004RDH7Y8/
When I put my mouse over the picture, it blows it up so I can see that the top three buttons (to the left of the screen) are needle positions. My best guess is that the highest button is for left needle position, next one down is center needle position, and third one down is right needle position.