Esta es una función que conseguí navegando no me acuerdo bien por donde. Fijate si te sirve (ojo que la función original decía pesos y la cambié para que diga colones, fijate que haya quedado bien)
Option Explicit
'Mauricio Baeza
mbs@inbox.net
'Samuel Monajaras
smonjaraz@hotmail.com
'Enero-97
'http://www.vbalym.netfirms.com
'Argumentos:
'Numero = Valor que deseamos convertir en texto
'Estilo = Formato de salida
' 1 = MAYUSCULAS
' 2 = minusculas
' 3 = Tipo Titulo
'Los valores negativos los convierte a positivos
'El valor minimo en 0, el valor maximo es 9,999,999,999,999.99
Public Function NumLetras(ByVal Numero As Double, ByVal Estilo As Integer) As String
Dim NumTmp As String
Dim c01 As Integer
Dim c02 As Integer
Dim pos As Integer
Dim dig As Integer
Dim cen As Integer
Dim dec As Integer
Dim uni As Integer
Dim letra1 As String
Dim letra2 As String
Dim letra3 As String
Dim Leyenda As String
Dim Leyenda1 As String
Dim TFNumero As String
If Numero < 0 Then Numero = Abs(Numero)
NumTmp = Format(Numero, "000000000000000.00") 'Le da un formato fijo
c01 = 1
pos = 1
TFNumero = ""
'Para extraer tres digitos cada vez
Do While c01 <= 5
c02 = 1
Do While c02 <= 3
'Extrae un digito cada vez de izquierda a derecha
dig = Val(Mid(NumTmp, pos, 1))
Select Case c02
Case 1: cen = dig
Case 2: dec = dig
Case 3: uni = dig
End Select
c02 = c02 + 1
pos = pos + 1
Loop
letra3 = Centena(uni, dec, cen)
letra2 = Decena(uni, dec)
letra1 = Unidad(uni, dec)
Select Case c01
Case 1
If cen + dec + uni = 1 Then
Leyenda = "Billon "
ElseIf cen + dec + uni > 1 Then
Leyenda = "Billones "
End If
Case 2
If cen + dec + uni >= 1 And Val(Mid(NumTmp, 7, 3)) = 0 Then
Leyenda = "Mil Millones "
ElseIf cen + dec + uni >= 1 Then
Leyenda = "Mil "
End If
Case 3
If cen + dec = 0 And uni = 1 Then
Leyenda = "Millon "
ElseIf cen > 0 Or dec > 0 Or uni > 1 Then
Leyenda = "Millones "
End If
Case 4
If cen + dec + uni >= 1 Then
Leyenda = "Mil "
End If
Case 5
If cen + dec + uni >= 1 Then
Leyenda = ""
End If
End Select
c01 = c01 + 1
TFNumero = TFNumero + letra3 + letra2 + letra1 + Leyenda
Leyenda = ""
letra1 = ""
letra2 = ""
letra3 = ""
Loop
If Val(NumTmp) = 0 Or Val(NumTmp) < 1 Then
Leyenda1 = "Cero Colones "
ElseIf Val(NumTmp) = 1 Or Val(NumTmp) < 2 Then
Leyenda1 = "Colon "
ElseIf Val(Mid(NumTmp, 4, 12)) = 0 Or Val(Mid(NumTmp, 10, 6)) = 0 Then
Leyenda1 = "de Colones "
Else
Leyenda1 = "Colones "
End If
'***************************************************************
'Nota: la funcion StrConv solo funciona en Excel2000 en adelante
TFNumero = TFNumero & Leyenda1
Select Case Estilo
Case 1
TFNumero = StrConv(TFNumero, vbUpperCase)
Case 2
TFNumero = StrConv(TFNumero, vbLowerCase)
Case Else
TFNumero = StrConv(TFNumero, vbProperCase)
End Select
TFNumero = "(" & TFNumero & Mid(NumTmp, 17) & "/100 M.N.)"
NumLetras = TFNumero
End Function
Private Function Centena(ByVal uni As Integer, ByVal dec As Integer, _
ByVal cen As Integer) As String
Dim cTexto As String
Select Case cen
Case 1
If dec + uni = 0 Then
cTexto = "cien "
Else
cTexto = "ciento "
End If
Case 2: cTexto = "doscientos "
Case 3: cTexto = "trescientos "
Case 4: cTexto = "cuatrocientos "
Case 5: cTexto = "quinientos "
Case 6: cTexto = "seiscientos "
Case 7: cTexto = "setecientos "
Case 8: cTexto = "ochocientos "
Case 9: cTexto = "novecientos "
Case Else: cTexto = ""
End Select
Centena = cTexto
End Function
Private Function Decena(ByVal uni As Integer, ByVal dec As Integer) As String
Dim cTexto As String
Select Case dec
Case 1:
Select Case uni
Case 0: cTexto = "diez "
Case 1: cTexto = "once "
Case 2: cTexto = "doce "
Case 3: cTexto = "trece "
Case 4: cTexto = "catorce "
Case 5: cTexto = "quince "
Case 6 To 9: cTexto = "dieci"
End Select
Case 2:
If uni = 0 Then
cTexto = "veinte "
ElseIf uni > 0 Then
cTexto = "veinti"
End If
Case 3: cTexto = "treinta "
Case 4: cTexto = "cuarenta "
Case 5: cTexto = "cincuenta "
Case 6: cTexto = "sesenta "
Case 7: cTexto = "setenta "
Case 8: cTexto = "ochenta "
Case 9: cTexto = "noventa "
Case Else: cTexto = ""
End Select
If uni > 0 And dec > 2 Then cTexto = cTexto + "y "
Decena = cTexto
End Function
Private Function Unidad(ByVal uni As Integer, ByVal dec As Integer) As String
Dim cTexto As String
If dec <> 1 Then
Select Case uni
Case 1: cTexto = "un "
Case 2: cTexto = "dos "
Case 3: cTexto = "tres "
Case 4: cTexto = "cuatro "
Case 5: cTexto = "cinco "
End Select
End If
Select Case uni
Case 6: cTexto = "seis "
Case 7: cTexto = "siete "
Case 8: cTexto = "ocho "
Case 9: cTexto = "nueve "
End Select
Unidad = cTexto
End Function
Espero que te sirva. Suerte.