Alert When Number of Rows with an "Open" Status Goes Above 300

Hi there! Has anyone tried this? We have one case for each row and they have basic open and closed statuses. Higher management wants to get involved in monitoring the list when the number of open cases goes above a count of 300. I added a hidden column with an if statement that will turn 1 when the number of open cases goes above 300 and if that happens, an automated workflow will alert the necessary people. It happened for the first time today and we all got the alert that open cases went above 300, but we have continued to get numerous emails all day as more and more new cases have been added. No one wants to keep getting the notification with each new case getting added (new cases automatically are considered open, so it keeps driving the open cases number up). Any thoughts or suggestions here?