Excel can restrict data entry to certain cells by using data validation , prompt users to enter valid data when a cell is selected, and display an error message when a user enters invalid data.

You can use data validation to restrict the type of data or values that users enter into cells. This is an advanced topic on data validation. For an introduction to data validation, and how to validate a cell or a range, see Add data validation to a cell or a range.

By adding data validation to controls in your form template, you can ensure that the data that you collect is accurate and consistent, and that it conforms to any standards that are already in use by your company.

You can insert a drop-down list of valid entries (also called a drop-down menu or drop-down box) in Excel to make data entry easier, or to limit entries to certain items that you define.

You can find cells in a workbook that contain data validation by using the Go To Special dialog box. On the Edit menu, point to Find, and then click Go To. Click Special. Select Data …

If you set up your list source as an Excel table, then all you need to do is add or remove items from the list, and Excel will automatically update any associated drop-downs for you.

On the Data tab, in the Data Tools group, click the arrow next to Data Validation, and then click Circle Invalid Data. Excel displays a red circle around any cells that contain invalid data.

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You can use the Validation Rule property and the Validation Text property of a form control to validate data that is input to that control and to help users who input data that is not valid.

On the Data tab, in the Data Tools group, click the arrow next to Data Validation, and then click Circle Invalid Data. Excel displays a red circle around any cells that contain invalid data.