You can also think of this as a graduated annuity. To get the fv first calculate the pv as follows:

pv = PV((1+r)/(1+g)-1, n, pmt)/(1+g)
fv = FV(r, n, 0, pv)

where

r = discount rate (interest rate)
g = growth rate of the payments
pmt = first payment amount
n = number of payments