Code:

---

var speed = 0.02;

action myEntity
{
   while (my != NULL)
   {
	if (key_space)   // start pan and tilt
	{
	   while(my.pan != youEntity.pan || my.tilt != youEntity.tilt)
	   {
  		vec_diff(temp,youEntity.x,my.x);
    		vec_to_angle(my.skill1,temp);
  		my.skill4 = ang(my.skill1 - my.pan);
  		my.skill5 = ang(my.skill2 - my.tilt);
  				  				
  		my.pan += speed * my.skill4 * time_step;
  		my.tilt += speed * my.skill5 * time_step;
  		wait(1);
	   }
        }
   }
		
   wait(1);
}

---

EDIT
----
Modified the while condition. Maybe split it into
two while-loop.