No less frequently than once during each period of three months, the trust institution administering a common trust fund shall determine the value of the securities in the common trust fund as of the dates set for the valuation thereof. No participation shall be admitted to or withdrawn from the common trust fund, except (i) on the basis of such valuation and (ii) as of such valuation date.
Ala. Code § 5-12A-10 (1975)