how to restrict data entry of selected fields in a pdf form to a single user

I'm new to creating forms in Adobe and have done pretty well so far now I've hit a wall and need help.   I created a form for my team to use to apply for educational funds. I'd like it to serve as a way for me to track each application through the layers of bureaucracy that includes multiple campuses and departments.  I created a section at the end called For Office Use Only and locked the cells. I sent my form to a tester but she could enter data in the locked cells.

How do I restrict specific cells in a form to editing by a single, designated user?

Thanks for your advice.