Whenever the court enters an order requiring the payment of spousal support, if the court anticipates the payment or any portion thereof is to be paid out of "disposable retired or retainer pay" as that term is defined in 10 U.S.C. § 1408, relating to members or former members of the uniformed services of the United States, the court shall specifically provide for the payment of an amount, expressed in dollars or as a percentage of disposable retired or retainer pay, from the disposable retired or retainer pay of the payor party to the payee party.