How to detect not collision?

I want something to happen when player collides with one sensor. But right after they stop colliding, I want to happen something else. How to do that?

Make an boolean attribute for your sensor actor in its events and set it true in when created event.
Then, make a collision event for checking the collision of player with sensor.
And then add an
if (boolean attribute)
set boolean attribute to false


do whatever you want her...