Some kind of trigger

Hello all and thanks for your time.
I want to know if there is some way to make/script some kind of
"trigger" or same thing in the simulator. I mean, let's say i want to
show a message on the player screen in case the car steps on a certain
area or stays in an area for a certain period of time. Is there a way
to do that? what should i read?

Thanks in advance

Pablo

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