how to restrict some values of product approval status in product cockpit for buyergroup

Hi All

I have two users Product Buyer and Product Manager . Product Manager can add/edit the product. As OOB provided in approval status attribute values are Check , UnCheck and Approved and unapproved . Now i want restrict only two values ( unapproved and approved) to display of approval status attribute for Product buyer. Does we have any idea how to restrict the attribute values