Check All Students NOT enrolled in a specific Season

We need an option to Robo-Mail and Robo-Text all students NOT enrolled in a specific Season. I would like to send emails/texts to students who have not yet registered for our Fall Season however our Summer and Fall Seasons overlap so currently this cannot be accomplished without first printing a report, and then selecting the students individually then sending the Email/Text. This is very inefficient and time consuming. Especially during fall registration as this is something I do 1-2 times per week in August and September. PLEASE HELP! Thank you!