How-To Geek on MSN

How to use the ISNUMBER function in Microsoft Excel

Master Excel’s most versatile logical gatekeeper to validate inputs, prevent math crashes, and automate complex spreadsheet ...
Hosted on MSN

Excel's data validation is far more powerful than just dropdowns — here's what it can actually enforce

Most people set up a dropdown list to make spreadsheets smarter with Excel's data validation. However, the Custom option in the Data Validation dialog accepts any formula that returns TRUE or FALSE, ...