Goals and Goals weightage not to be updated by Employee and Manager

Hi

This is a scenario where the Goal Objective Process is completed and Goals are synced in performance document, Here as per Business Requirements the Goals which has been added during Goal Setting process should not be removed,edited or added in performance doc by Employee and Line Manager weightage however is a seeded functionality which is managed

This is an important check we need to have and a showstopper please let us know how this can be implemented and if there are any seeded or custom approach we can take on this