Cambiar de números a letras en excel

Crea un modulo enel editor de macros y pon este código
Luego en la celda que quieras colocas =pesos(y el numero que quieras cambiar).
Espero te sirva
'------------ INICIO DE LA FUNCION PESOS-----------------------------------
'Function Pesos(Number As Single) As String
'Comentado el 27/10/2008: La siguiente línea corrige el error de los decimales
'en cantidades grandes, gracias a Any por la corrección.
Function Pesos(Number As Double) As String
Const MinNum = 1#
Const MaxNum = 4294967295.99
Dim Numbers, Tenths, Result As String
Numbers = array("cero", "un", "dos", "tres", "cuatro", "cinco", "seis", "siete", "ocho", "nueve", "diez", "once", "doce", "trece", "catorce", "quince", "dieciseis", "diecisiete", "dieciocho", "diecinueve")
Tenths = Array("CERO", "DIEZ", "VEINTE", "TREINTA", "CUARENTA", "CINCUENTA", "SESENTA", "SETENTA", "OCHENTA", "NOVENTA")
If (Number >= MinNum) And (Number <= MaxNum) Then
Result = RecurseNumber((Fix(Number)))
If Round((Number - Fix(Number)) * 100) < 10 Then
Result = Result + " PESOS"
Else
Result = Result + " " + Str(Round((Number - Fix(Number)) * 100)) + "PESOS"
End If
Else
Result = "Error, verifique la cantidad."
End If
Pesos = Result
End Function
Function RecurseNumber(N As Long) As String
Dim Numbers, Tenths
Numbers = array("cero", "un", "dos", "tres", "cuatro", "cinco", "seis", "siete", "ocho", "nueve", "diez", "once", "doce", "trece", "catorce", "quince", "dieciseis", "diecisiete", "dieciocho", "diecinueve")
Tenths = Array("CERO", "DIEZ", "VEINTE", "TREINTA", "CUARENTA", "CINCUENTA", "SESENTA", "SETENTA", "OCHENTA", "NOVENTA")
Hundrens = array("cero", "ciento", "doscientos", "trescientos", "cuatrocientos", "quinientos", "seiscientos", "setecientos", "ochocientos", "novecientos")
Dim Result As String
Select Case N
Case 0
Result = ""
Case 1 To 19
Result = Numbers(N)
Case 20 To 99
If N Mod 10 <> 0 Then
Result = Tenths(N \ 10) + " Y " + RecurseNumber(N Mod 10)
Else
Result = Tenths(N \ 10) + " " + RecurseNumber(N Mod 10)
End If
Case 100 To 999
If N \ 100 = 1 Then
If N = 100 Then
Result = "CIEN" + " " + RecurseNumber(N Mod 100)
Else
Result = Hundrens(N \ 100) + " " + RecurseNumber(N Mod 100)
End If
Else
Result = Hundrens(N \ 100) + " " + RecurseNumber(N Mod 100)
End If
Case 1000 To 999999
Result = RecurseNumber(N \ 1000) + " MIL " + RecurseNumber(N Mod 1000)
Case 1000000 To 1999999
Result = RecurseNumber(N \ 1000000) + " MILLON " + RecurseNumber(N Mod 1000000)
Case 2000000 To 999999999
Result = RecurseNumber(N \ 1000000) + " MILLONES " + RecurseNumber(N Mod 1000000)
Case 1000000000 To 4294967295#
Result = RecurseNumber(N \ 1000000000) + " BILLONES " + RecurseNumber(N Mod 1000000000)
End Select
RecurseNumber = Result
End Function