Matrix table question validation

Hi, here is my survey flow. Employee fills out a survey which has a Matrix Table question (constant sum). Then via Actions I send an email with the link to the Supervisor to view/edit the Employee's responses. When it goes to the Supervisor, I've a Y/N question at the top followed by the Matrix Table question (constant sum) prepopulated with the responses submitted by the Employee.
Now the Supervisor is given the Y/N question to see if they agree with the Employee's responses in the Matrix table. If the Supervisor selects 'Y' then the Matrix table question should become uneditable and if the Supervisor selects 'N' they must make updates to the Matrix table responses.
I guess it can be done using JS validation. How to validate a Matrix Table question (constant sum) using JavaScript? Like if they select 'Y' then the Matrix table question should be disabled and if they select 'N' they MUST update the Matrix table and can't proceed w/o updating. Please let me know. Thanks.