This example uses the FV function to return the future value of an investment given the percentage rate that accrues per period (APR / 12), the total number of payments (TotPmts), the payment (Payment), the current value of the investment (PVal), and a number that indicates whether the payment is made at the beginning or end of the payment period (PayType). Note that because Payment represents cash paid out, it's a negative number.
FV([APR] / 12, [TotPmts], -[Payment], -[PVal], [PayType])