If you use Excel spreadsheets to collect data from other people, but find that they often fill your carefully-planned cells with the wrong kind of information, data validation can help.
This tool lets you restrict specific cells to only allow properly-formatted data. If someone enters anything that’s not supposed to be there—like “lunch at airport” instead of “$15.68” on an expense report—Excel rejects the input until they get it right. Think of it as a passive-aggressive way to make sure people don’t waste your time.
