Scratch

There are Many, MANY tutorials about how to scroll. i just spotted a project tutorial on how to  use scroll X. I'll post details soon.

~Geekish

It's not scrolling but creates the impression of moving to a new area:

For your moving sprite:

Forever if X position is >230               <-  (practically off-screen)
move -450 steps
broadcast "next background" and wait

(the stage changes,and other sprites move into their places)

Might not be what you're looking for,but it works well enough for me 
The only problem you may have is with the enemies,though-they may not "scroll" easily,but you could keep it to them appearing and disappearing in different places when they receive "next background"

It also works the other way around :at -230,you could move back a background to a previous area

It doesn't:sorry, was that what you were looking for?

The background doesn't scroll but changes when the character moves to the edge of the screen.
The character reappears at the opposite side of the screen in a new environment,but from the sound of things I don't think you're looking for this kind of scene jump!