Print Ackermann(1, 2)

    Function Ackermann(m, n)
        Select Case
            Case (m < 0) Or (n < 0)
                Exit Function
            Case (m = 0)
                Ackermann = (n + 1)
            Case (m > 0) And (n = 0)
                Ackermann = Ackermann((m - 1), 1)
            Case (m > 0) And (n > 0)
                Ackermann = Ackermann((m - 1), Ackermann(m, (n - 1)))
        End Select
    End Function