Hey i made an example of IWBTG like scrolling, hope you like it.
Edit: Ok so just to make know you got it.
Gray box is only to center view on it.
Playfield is the multiply of 3x2 fields of dimensions 320:240.
In order to make a skipping to other field you must do this formula
floor(Sprite.X/320)*320+160[/code:1o6imz08]
Where Sprite is our player, the floor is needed to determine on which field you are so if you are in less than 320 then the value is 0 if your even further >640 then its 2 and so on, also the +160 is to center the position. The y scrollin is just the same as x just change 320 to 240 becouse height is lower.