So I have a airfreshner (airwick sense and spray) and it has a motion sensor that has a range of 6 meters how do I decrease is for it to be around 15 cm so only when I pass my hand in front of I it will work. I need the mechanism for my experiment

There is no easy way to do this as the sensors would need reprogramming.

There is no easy way to do this as the sensors would need reprogramming.
What about using another sensor?