No this is not possible. Not directly to be exact.
Event functions get the "my" pointer of the entity which triggered the event.
so to pass your 5 to the event, do this:
Code:
function dothis(var passinto){
	if (event_type == EVENT_IMPACT){		
		beep();
                wait(my.skill80);
	}	
}
action elevator_move(){
	my.emask |= ENABLE_IMPACT;
	my.event = dothis;
	my.skill80 = 5;
}

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