How to make transparent only colliding part of object?

Hi! I want to make something like an x-ray border and when some object (sprite) falls from the sky through that border, it will become transparent on colliding part. For example, now I'm just using the alpha of the colliding object to make it fully transparent, but I need more complex effect. Here is the screen:

I want to make the black cube inside sprite transparent at the position of the green bar (and green bar must be transparent at the cube position)