I did this once by using the A* pathfinding kit here and making the target object follow the mouse that skates across the floor, at a speed high enough to look instant while using rigidbodies to handle collisions and stop the box when it hit something despite the mouse target being inside that object.
Without using physics I'm not sure. You could also get the angle between the target and the object, then apply force on that angle but it would require a lot of tweaking it make it work.
That's the only ideas I really have.