Issue
I need to identify repeating values in a column (ID numbers) in a Google Sheet that contains user input from a form. I also want to compare the row index and mark the repeated entry with the text "Repeated" in a specific column. This will help me ensure that no employee can have two requests at once, preventing double booking of leave or day-off requests.
Resolution
We have a sample app that validates if an entry is already present in the database before submitting it. You can fork the app to check the code.