Well I believe you would need to be able to get the position of the virtual "collision" box around a Object, Compare the X,Y of it, And then somehow get the width of from the center to the top of the object, and then use that width to check the Z. That would be needed because of when moving an object, you move it from its center.
Now, I believe that is not possible with the current functions PAWN has to offer, it would also take a lot of performance up :\