Access: función para cambiar de números a letras

He corregido lo de cincocientos
Y añaido una nueva función con céntimos seria:
NumerosEurosALetras(501.21, False,"euro","centimo")
NumerosEurosALetras(501, False,"dolar","centavo")
NumerosEurosALetras(501, False,"peso","centavo")
El único problema es la coma decimal... que en mi ordenador
el la "," (aunque al escribir los números los escribo con "." )
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Código a pegar en un modulo
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Public Function NumerosConComaALetras(ByVal NumberStr As String) As String
Dim nTemp
nTemp = InStr(NumberStr, ",")
If nTemp = 0 Then
NumerosConComaALetras = NumerosALetras(NumberStr, False)
Else
NumerosConComaALetras = NumerosALetras(Left(NumberStr, nTemp - 1), False) & " coma " & _
NumerosALetras(Mid(NumberStr, nTemp + 1), False)
End If
End Function
Public Function NumerosEurosALetras(ByVal NumberStr As String, Optional lFemenino = False, Optional cMoneda = "euro", Optional cCentimos = "céntimo") As String
Dim nTemp, nDecimales
nTemp = InStr(NumberStr, ",")
If nTemp = 0 Then
NumerosEurosALetras = NumerosALetras(NumberStr, lFemenino, cMoneda)
Else
nDecimales = Len(Mid(NumberStr, nTemp + 1))
Select Case nDecimales
Case 0
NumerosEurosALetras = NumerosALetras(NumberStr, lFemenino, cMoneda)
Case 1, 2 'centimos'
If nDecimales = 1 Then
NumberStr = NumberStr & "0"
End If
NumerosEurosALetras = NumerosALetras(Left(NumberStr, nTemp - 1), lFemenino, cMoneda) & " con" & _
NumerosALetras(Mid(NumberStr, nTemp + 1), lFemenino, cCentimos)
Case Else
NumerosEurosALetras = NumerosALetras(Left(NumberStr, nTemp - 1), False) & " coma " & _
NumerosALetras(Mid(NumberStr, nTemp + 1), False) & " " & cMoneda & _
IIf(InStr("aeio", Right(cMoneda, 1)) = 0, "e", "") & "s"
End Select
End If
End Function
Public Function NumerosALetras(ByVal NumberStr As String, Optional lFemenino = True, Optional cMoneda = "") As String
Dim z As String, x As String, Temp As String, c As String
Dim a As Integer, b As Integer, i As Integer
Dim iPos As Integer
Dim data(9, 3) As String
data(0, 0) = "uno"
data(1, 0) = "dos"
data(2, 0) = "tres"
data(3, 0) = "cuatro"
data(4, 0) = "cinco"
data(5, 0) = "seis"
data(6, 0) = "siete"
data(7, 0) = "ocho"
data(8, 0) = "nueve"
data(9, 0) = "diez"
data(0, 1) = "cien"
data(1, 1) = "diez"
data(2, 1) = "veinte"
data(3, 1) = "treinta"
data(4, 1) = "cuarenta"
data(5, 1) = "cincuenta"
data(6, 1) = "sesenta"
data(7, 1) = "setenta"
data(8, 1) = "ochenta"
data(9, 1) = "noventa"
data(0, 3) = "diez"
data(1, 3) = "once"
data(2, 3) = "doce"
data(3, 3) = "trece"
data(4, 3) = "catorce"
data(5, 3) = "quince"
data(6, 3) = "dieciséis"
data(7, 3) = "diecisiete"
data(8, 3) = "dieciocho"
data(9, 3) = "diecinueve"
'remove redundant spaces
'NumberStr = Trim( Replace(NumberStr, ",", ""))
NumberStr = Trim(NumberStr)
a = Len(NumberStr)
Temp = NumberStr
If Val(NumberStr) = 0 Then
NumerosALetras = "cero"
Exit Function
End If
'get rid of any decimals
iPos = InStr(Temp, ",")
If iPos > 0 Then Temp = Left(Temp, iPos - 1)
While ((a Mod 3) <> 0)
Temp = "0" & Temp
a = Len(Temp)
Wend
NumberStr = Temp
For i = a - 2 To 1 Step -3
b = b + 1
Temp = Mid(NumberStr, i, 3)
z = ""
' "Intelligent" routines
'------------------------
If Temp <> "000" Then
If Temp = "100" Then
z = "cien"
Else
c = Left(Temp, 1)
If c <> "0" Then
If c = "1" Then
z = "ciento"
ElseIf c = "5" Then
z = " quinientos"
ElseIf c = "7" Then
z = " setecientos"
ElseIf c = "9" Then
z = " novecientos"
Else
z = " " & data(Val(c) - 1, 0) & "cientos"
End If
End If
c = Mid(Temp, 2, 1)
If c <> "0" Then
If c <> "1" Then
z = z & " " & data(Val(c), 1)
Else
z = z & " " & data(Val(Right(Temp, 2)) - 10, 3)
End If
End If
End If
If Right(Temp, 1) <> "0" And Mid(Temp, 2, 1) <> "1" Then
z = z & IIf(z = "", "", " y ") & data(Val(Right(Temp, 1)) - 1, 0)
End If
End If
'------------------------
If z <> "" Then
Select Case b
Case 1:
x = z
Case 2:
If z = "uno" Then
x = "mil" & x
Else
x = z & " mil" & x
End If
Case 3:
If z = "uno" Then
x = "un millón " & x
Else
x = z & " millones " & x
End If
Case 4:
If z = "uno" Then
x = "mil millones " & x
Else
x = z & " mil millones " & x
End If
Case 5:
If z = "uno" Then
x = "un billón " & x
Else
x = z & " billones " & x
End If
Case Else:
Exit Function
End Select
End If
Next
'correción de genero
If x = "uno" Then
x = IIf(lFemenino, "una", "un")
ElseIf Right(x, 3) = "uno" Then
x = Mid(x, 1, Len(x) - 3) & IIf(lFemenino, "una", IIf(cMoneda = "", "uno", "un"))
ElseIf Right(x, 3) = "tos" And lFemenino Then
x = Mid(x, 1, Len(x) - 3) & "tas"
End If
If cMoneda <> "" Then
x = x & " " & IIf(Val(NumberStr) <= 1, cMoneda, cMoneda & IIf(InStr("aeio", Right(cMoneda, 1)) = 0, "e", "") & "s")
End If
NumerosALetras = x
End Function

Me sale error en la ejecución en
z = " " & data(Val(c) - 1, 0) & "cientos"
La dar numerosEurosALetras(501.25, False,"peso","centavo")
usando el "." en vez de la coma
Saludos.
Miguel Paniza