If you are designing an excel sheet for other users to enter data, or even for your own use, it is a good idea to use the data validation feature to insure that only correct data will be entered. hear is how you do it:
- Select the cell you want to validate.
- On the Data menu, click Validation, the Data Validation dialogue box will be shown.

- Click the Settings tab.
- Specify the type of validation you want. Suppose you have a numeric value and you want to allow only values between 1 and 99, then:
- In the Allow combo box select ‘Decimal’.
- In the Data combo box select ‘Between’.
- In the Minimum edit box enter ‘1’.
- In the Maximum edit box enter ‘99’.
To show an error message when an invalid data is entered:
- Click the Error Alert tab.
- Fill the Title and Error Message edit boxes with appropriate text. (See example).

To remove data validation, click the Clear All button in the Settings tab.
Applies to : Excel 2003