Validate and throw error message based on the selected dropdown value

[Archana]

I have a dropdown field with options Yes and No. 

If the user, selects No, I need to populate an error message. I tried the validation rules but I am clearly doing something wrong. 

It worked fine when using radio buttons 

[marc -Collabello--Phase Locked-]

Hi @Archana ,

Can you provide an example of what you are trying to do?