..
 set(my,LIGHT);
 my.lightrange = 0;
 my.red = 255;
 my.green = 1;
 my.blue = 1;
 ..

define selected skill100

void selection_sprite(){ // fex a circle sprite
	set(my,PASSABLE|TRANSLUCENT);
	my.tilt += 90;
	while(you){	
                vec_set(my.x, you.x);	
		if (you) if (!you.selected) break;
		wait(1);
	}
	wait(1);
	ptr_remove(me);
}

..
my.selected = 1;
ent_create("circle.tga", vector(my.x, my.y, my.z), selection_sprite);

..
wait(-1);
my.selected = 0;

var selected = 0;

void highlight_me(){
   selected = 0;
   wait(1);
   selected = 1;
   while (selected){
      //highlightstuff
      wait (1);
   }
}

set (my, FLAG1);
 or
 my.selected = 1;

var selected = 0;
action blabla...
..

..
for(you = ent_next(NULL); you; you = ent_next(you)) 
  {
    if(is(you, FLAG1))    
    	reset (you, FLAG1);
  }
..