Using Data Validation

One of the tools provided with Excel allows you to ensure that the data in your workbook is within specific bounds, and therefore of a higher quality than unchecked data. This tool is referred to as data validation, and it allows you to set the bounds applicable to your data.

For example, lets assume you are creating a simple worksheet to calculate the future value of a sum, and that in order to do so, you need input from the user (regular deposit, interest rate, and months). You may want to place limits on the information which can be used in the worksheet. For example, you may want to make sure the user always enters an interest rate between 2.5% and 25%. To do this, all you need to do is follow these steps:

1. Select the cell where the user enters the interest rate.
2. Choose the Validation option from the Data menu. Excel displays the Data Validation dialog box. (Click here to see a related figure.)
3. Use the Allow drop-down list to specify what type of number you want to allow. In this instance choose the Decimal option, indicating you want the user to be able to enter a decimal value. The dialog box changes a bit so you can specify the type of data to be entered.
4. Use the Data drop-down list to specify how you want the information the user is entering to be compared in your validation rule. You can pick settings such as "between" and "greater than." In this case, you should choose "between," since you want to specify a range for the interest rate.
5. Specify a minimum and maximum acceptable value for the cell. In the case of this example, the minimum should be .025 (which can also be entered as =2.5%) and the maximum should be .25 (which can be entered as =25%).
6. Click on the OK button.

Effectively, you have set a validation rule that says "accept any decimal value that is between 2.5% and 25%." If the user tries to add information to the cell that is outside the range you specified, they are notified that they have made an error and a different value must be entered.