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
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.