how to destroy items that collide with our block

(first of all I point out that I am using a translator so I apologize that you are not really clear)

here is what i would like to do i would like that when an element collides with the top of my 3d block it is automatically destroyed like a garbage can i explain myself a little more clearly when an element collides with the top of my 3D block it must be destroyed a bit like lava but only on the top if anyone has a solution I'm interested thank you and I hope to have an answer thank you very much for reading and goodbye..