Accept a prompt in Excel Online in Data Validation

Hi Experts,

I am using this formula in Data Validation in Excel Online:

=SEARCH(", ",B10)

The idea is to force the user to enter a name with a COMMA.

But when i try to accept the formula Excel throws an error saying:

"This formula currently evaluates to an error. Do you want to continue?"

I would like to say Yes but don't know where to click it..

Any idea?

There are instructions at the top of the page explaining how to attach your sample workbook (yellow banner: HOW TO ATTACH YOUR SAMPLE WORKBOOK). Screenshots are of little practical use as we cannot manipulate them.

A good sample workbook has just 10-20 rows of representative data that has been desensitised. It also has expected results mocked up, worked examples where required, relevant cells highlighted and a few explanatory notes.