Limit Sheet Rows Available or Limit Form Submissions

Hi i'm trying to manage an event using SmartSheet. I have 4 sessions and each session can only have up to 30 registrants per session.

What i currently have is a single form with all users information included. Users will come into this form, and in a single column, I have the options for the 4 sessions. In this column, they will select a session 1-4. I have then set up an automation workflow to notify me when the number of individuals registered for any session reaches 30 - once 30 is reached, I have to go into the column with the session options and remove that session.

Is there a safer way/better way to do this that can place a cap on how many people can register for a particular session? I thought of creating 4 separate sheets and limiting each sheet to only 30 rows (1 row for each person to register in) but there is no way to limit rows in SmartSheet.

Even with SmartSheet's form capabilities, there is no way to limit the number of submissions based on any criteria. What is the best way to handle events in SmartSheet while being able to limit the number of registrants per event?