You will get the answer from Para 26(6) of the scheme, which is given as follows:
"Notwithstanding anything contained in this para, an officer not below the rank of APFC may, on joint request in writing, of any employee to which this scheme applies and his employer, enroll such employee as a member or allow him to contribute more than Rs. 6500 of his pay per month if he is already a member of the Fund. Thereupon, such employee shall be entitled to the benefits and shall be subject to the conditions of the Fund, provided that the employer gives an undertaking in writing that he shall pay the administration charges payable and shall comply with all statutory provisions in respect of such employee."
Regards.