1. Open Excel and select a range of cells to which you want to apply the data validation. For example, select cells A1 through A10. With the cells selected, click the “Data” menu and choose “Validation.”
2. Change the Allow criteria to “List” in the validation criteria. In the Source field, add the values you want to see in the drop-down list. Enter the values separated by a comma only. Do not include spaces. For example, enter “Yes,No,Maybe” to see those three options in the drop-down list.
3. Modify the input message so other users see a friendly reminder telling them what you are looking for in these cells. Click on the “Input Message” tab. Make sure the “Show Input Message When Cell is Selected” option is checked. In the title field, add a title for your custom message. Type your custom message in the “Input Message” field.
4. Modify the error alert message so users see a error alert if they input the wrong type of information. Click on the “Error Alert” tab. Place a check mark in the “Show Error Alert After Invalid Data Is Entered” option. Change the style to “Stop” if you want the message to stop users from inputting invalid data. In the title field, add a title for your custom message. Type your custom message in the “Error Message” field. Click “OK.”
5. Test your data validation by clicking on cell A1. You will see a drop-down list appear with the options Yes, No and Maybe. You should see the input message you specified. Try typing in the word “PDF.” The custom error message will appear. The invalid value will not be retained and you will get the prompt to “Retry” and enter a correct value.