Take a look at the endless runner example that comes with C2. After examining it, I think you could modify that example so the background only runs when the player is moving. It's pretty easy to follow. If you need som more help after examining it, post back here.
Thanks. Each time the player is NOT moving I set the backdrop's timescale to 0 and if the player is moving then I set it to 1. Is this a performance effective way to solve this problem?