Great it works!
I would never thought that you could mix entity with defines ^^

Fore those who are interested:

Code:
function AIfriendly_find_target()
{
	var closestTarget_dist;
	for(you=ent_next(NULL); you!=NULL; you=ent_next(you))
	{
		if ((you != my) && (you.team != my.team) && (you.health>0))
		{
			if(my.the_target ==NULL)
			{   
				my.the_target = you;
				ENTITY* enemy_target = my.the_target;
				closestTarget_dist = vec_dist(you.x, me.x);  
			}
			else
			{
				if(vec_dist(you.x, me.x) < closestTarget_dist)	
				{   
					my.the_target = you;
					ENTITY* enemy_target = my.the_target;
					closestTarget_dist = vec_dist(you.x, me.x); 
				}
			}
		}
	}
}


Thank you!