How do you validate data in MS Excel?

For a range of cells that you choose, you can create criteria that must be satisfied for entering data into those cells. Any data outside the criteria will be flagged as an error.

Highlight a number of cells in a column and click the Data Validation toolbar item shown

 

As seen here a few cells have been highlighted and the Data Validation clicked. This will bring up the Data Validation form as shown. I set up the criteria as shown here allowing whole numbers between 1 and 200.

 Here attempting to enter 30.5 in one of the highlighted cells brings up this error message.

 

 Here entering a number greater than 200 brings up the message.

 You could also tailor the error message instead of the default one seen above by configuring the Error Alert tab as shown.

 Now you will see your custom message as shown.

 

This is the Office version used in this post.