Pre-enrollment add/drop

<p>basically, there is this pe class i want to take, but it is full... so i have been refreshing the page constantly throughout the day, hoping that the blue closed box would turn into a green open circle. is this what I should be doing, waiting for someone to drop the class, so i can immediately get the spot? am i doing this process right? also, I know my chances are slim to none, but there are people who decide to change their pe classes during pre-enrollment, right?</p>