or give everything a different type
so have
#define _type skill1
#define actors 1
#define bushes 2
#define water 3
//etc...
then in the action for each have
action act_actor(){
my._type = actors;
}
then everytime you need to change it call
function alpha_actors()
{
you = ent_next(NULL);
while(you){
if(your._type == actors){
set(you,TRANSLUCENT); // make entity invisible
}
you = ent_next(you); // get next entity
}
}
hope this helps
*code untested*