Como escrever número por extenso no Excel (valor em reais)

Function Ate999(ByVal n As Long) As String
    Dim u, d, c, t As String, r As Long
    u = Array("", "um", "dois", "três", "quatro", "cinco", "seis", "sete", "oito", "nove", "dez", "onze", "doze", "treze", "quatorze", "quinze", "dezesseis", "dezessete", "dezoito", "dezenove")
    d = Array("", "", "vinte", "trinta", "quarenta", "cinquenta", "sessenta", "setenta", "oitenta", "noventa")
    c = Array("", "cento", "duzentos", "trezentos", "quatrocentos", "quinhentos", "seiscentos", "setecentos", "oitocentos", "novecentos")
    If n = 100 Then Ate999 = "cem": Exit Function
    t = c(n \ 100)
    r = n Mod 100
    If r > 0 And r < 20 Then
        If t <> "" Then t = t & " e "
        t = t & u(r)
    ElseIf r >= 20 Then
        If t <> "" Then t = t & " e "
        t = t & d(r \ 10)
        If r Mod 10 > 0 Then t = t & " e " & u(r Mod 10)
    End If
    Ate999 = t
End Function

Function Extenso(ByVal valor As Double) As String
    Dim centavos As Double, reais As Long, cent As Long
    Dim mi As Long, mil As Long, un As Long, t As String
    centavos = Int(valor * 100 + 0.5)
    reais = Int(centavos / 100)
    cent = centavos - reais * 100
    mi = reais \ 1000000
    mil = (reais \ 1000) Mod 1000
    un = reais Mod 1000
    If mi > 0 Then
        t = Ate999(mi)
        If mi = 1 Then t = t & " milhão" Else t = t & " milhões"
    End If
    If mil > 0 Then
        If t <> "" Then
            If un = 0 And (mil < 100 Or mil Mod 100 = 0) Then t = t & " e " Else t = t & " "
        End If
        If mil = 1 Then t = t & "mil" Else t = t & Ate999(mil) & " mil"
    End If
    If un > 0 Then
        If t <> "" Then
            If un < 100 Or un Mod 100 = 0 Then t = t & " e " Else t = t & " "
        End If
        t = t & Ate999(un)
    End If
    If reais > 0 Then
        If reais Mod 1000000 = 0 Then t = t & " de"
        If reais = 1 Then t = t & " real" Else t = t & " reais"
    End If
    If cent > 0 Then
        If t <> "" Then t = t & " e "
        t = t & Ate999(cent)
        If cent = 1 Then t = t & " centavo" Else t = t & " centavos"
    End If
    If t = "" Then t = "zero reais"
    Extenso = t
End Function