Explanation
Data validation rules are triggered when a user adds or changes a cell value.
The COUNTIF function simply counts occurrences of the value in the list.
Any count greater than zero will pass validation.
COUNTIF can be used to count…
Data validation exists in list
Note: Excel has a built-in data validation rules for dropdown lists. This page explains how to create a your own validation rule for lists when you don't want the dropdown behavior. To allow only values from a list in a cell, you can use data validation with a custom formula based on the COUNTIF function. In the example shown, the data validation applied to C5:C9 is: =COUNTIF(colors,C5)>0
