How do I make an event only calculate once?

In this situation whene a square is 7pixel near an other square having a special variable, the square detected should change colour. For this I use LOS, but the way my event is structured, each square with special variable checks every ticks (i guess) if there's an other one near which obviously cause lag.

So I would need to fix this by only calculating if there's squares near whene a button is clicked but also have the colours display until it updates.

Thank you

I don't know if this is the right context to suggest but wouldn't "System --> Trigger Once While True" help in these scenarios?

"Trigger once" should never be used with objects that have multiple instances.

jawad2heaven Simply create a sub-event in "On left button clicked", and move the second event there. You won't even need the "clicked" variable.

And you can use "On object clicked" instead of checking if cursor is over the sprite.

Thank you, it worked