Function ASS(N, B)
    Dim A(15)
    A(1) = Exp(-B) / B
    If N = 1 Then GoTo 11
    DB = 1# / B
    For I = 2 To N
        A(I) = A(1) + DB * (I - 1) * A(I - 1)
    Next I
11  ASS = A(N)
End Function