You can do it if you replace the boxes with sprites.
The box object doesn't have a 'collision mode' condtion.
+ System: Always (every tick)
-> Sprite: Set horizontal speed : 100
+ System: For each SpriteBOX
+ SpriteBOX: Height Greater than 45
-> SpriteBOX: Set collision mode to None
+ Sprite: Sprite overlaps SpriteBOX
+ SpriteBOX: Height Less than 45
-> Sprite: Push out of SpriteBOX : Opposite angle
Hope this helps.