1. Open an Excel spreadsheet. Click in an empty cell and type the first item for the drop-down list. Press 'Enter' and then type the second entry. Continue doing this for all entries in the list you need.
2. Click the cell where you want a drop-down list. Click and drag across multiple cells to highlight all of them if you want them all to have the drop-down list.
3. Click the 'Data' tab on the Ribbon and then click 'Data Validation' in the Data Tools group.
4. Click the drop-down menu under the Settings tab and select 'List.' Click the button beside the Source text box to open the reference box. Click and drag over the cells that contain the options for the menu to select all of them, and then click the button beside the selected area on the dialog box. Make sure both the 'Ignore blank' and 'In-cell drop-down' options are checked.
5. Click the 'Error Alert' tab. Type 'Invalid Entry' in the Title text box. Type 'You have made an invalid selection. Please try again' in the Error Message text box. If a user does not select an option from the drop-down list, this error message flashes on the screen.
6. Click the 'OK' button to close the Data Validation dialog box. The drop-down list appears in all of the highlighted cells. Save the spreadsheet.