(a) The effect of provisions of this chapter may be varied by agreement of the parties made at any time before or after commencement of an action, commencement of a distribution proceeding, or the entry of judgment.
(b) The parties may agree upon the money to be used in a transaction giving rise to a foreign-money claim and may use different moneys for different aspects of the transaction. Stating the price in a foreign money or for a particular transaction does not, of itself, require the use of that money for other aspects of the transaction.