Scratch

Could you supply some more details of what you are trying to do?  Are you trying to make a scrolling background or just a background that changes to a different scene when something happens?   

If all you want is a stage background to change when a sprite does something...the easiest way to do that is with Broadcast messages.  Have the Sprite Broadcast a message (you make up the message name) when you want the stage to change.  Then, on in the Stage script area, you set up a When I Receive hat block with the same message name and connect a Next Background block below it.  That should do it.