try this :
Code:
ENTITY* t_trigger;

var trig_percentage;

action trigger_switch()
{
	t_trigger = me; //this is a pointer defining the entity listed at the top

	while(1)
	{
		if (key_enter)
		{
			if(trig_percentage = 1)
			{
				trig_percentage %= 100;
				trig_percentage += 2*time_step;
				ent_animate(t_trigger, "on", trig_percentage, ANM_SKIP);
				trig_percentage = 0;
			}
			else
			{
				trig_percentage %= 100;
				trig_percentage += 2*time_step;
				ent_animate(t_trigger, "off", trig_percentage, ANM_SKIP);
				trig_percentage = 1;				
			}
			
			
		}
		wait(1);
	}

}



the wait function must be in while else your engine window will freeze