On the indication of the amount of certificate of origin in

Note: A is a domestic manufacturer; B is a Hong Kong offshore company(intermediary); C is a foreign customer. The trade process is: middleman B and factory a purchase products directly sold to C, now C requires B to provide certificate of origin, so B requires a certificate of origin; but now the problem is: the certificate of origin requires the amount of money, now B does not want to let a know the price sold to C, at the same time, does not want to let C know the price to buy with A. is there any way to avoid this situation?