4 channel digital scope
No, you can't view all three at once with a two channel oscilloscope. However, you could trigger on 1, capture 1 + 2 and save #2. Then, use the same trigger but capture 1 + 3 and you could compare them all.

This will only work if it's repeatable, though. If you have 1-off signals that change every cycle or look different every time you'll need a 4-channel scope.