The prospective designation in a will or other instrument of an affiliated bank of a subsidiary trust company as fiduciary is also considered a designation of the company as fiduciary and confers on the company any discretionary power granted in the instrument unless:
(1) the bank and company agree in writing to have the designation of the bank as fiduciary be binding; or
(2) the creator of the fiduciary account, by appropriate language in the document creating the account, provides that the account is not eligible for substitution under this chapter.