A problem about moving two objects at the same time.

Hello all I'm with a simple problem, I want to make every click on an object should move this object clicked to a destination if there is no object "cube" in place, and if there is already another object in the same target location this Object must move to the place where the object was clicked and the object that was clicked must move to the destination, I have three cubes I want to make this system of cubes moving to the destination and the one that is already in the destination should move to the place where it is The object that was clicked.

I attached the .blend file that illustrates my problem, I will be very grateful to you that I assist in this small project.