Can Not Applicable (N/A) be restricted to only 3 times while rating Competencies ?

Summary:

The client has provided a list of 12 competencies that would be 'fixed' in the template i.e. for everyone these 12 competencies would show. However they want to restrict the N/A option to only 3 times. i.e. The evaluator (self/manager) shouldn't be able to put N/A in more than 3 competencies for each performance document.

Content (required):

There are 5 rating levels to select from ('Exceptional' to 'Did not achieve the results') with the 6th option in the dropdown as Not Applicable (N/A). How can we restrict the N/A to a maximum of 3 ? (out of 12 competencies)

Version (include the version you are using, if applicable):