Microsoft Excel's Data Validation tool lets you add a drop-down list to a cell based on existing data in a column. However, how this works depends on whether the source data is part of a formatted ...

Go to the Data tab on the ribbon, then click Data Validation in the Data Tools section. In the Data Validation window, select ...

Set up rules to restrict data entry to specific formats, ranges, or value types For example, you could require that a cell accepts only whole numbers between 1 and 100, or that a date field allows ...