Finnally finished the code and got around the problem of:

1000 - is just "mil" not "Un Mil"
1001 is "mil uno" not "Un Mil Uno".


Function LoTioHablaBolivares(ByVal MyNumber, Sep, Mon)
          Dim Dollars, Cents, Temp
          Dim DecimalPlace, Count
          Dim origNumLen, origNum
          
          ReDim place(9) As String
          place(2) = " Mil "
          place(3) = " Millon(es) "
          place(4) = " Billones "
          place(5) = " Trillones "

          ' String representation of amount.
          MyNumber = Trim(CStr(MyNumber))
          origNumLen = Len(MyNumber)
          origNum = MyNumber
          
          ' Position of decimal place 0 if none.
          If Sep = "." Then DecimalPlace = InStr(MyNumber, ".")
          If Sep = "," Then DecimalPlace = InStr(MyNumber, ",")
          
          ' Convert cents and set MyNumber to currency amount.
          If DecimalPlace > 0 Then
              Cents = GetTens(Left(Mid(MyNumber, DecimalPlace + 1) & _
                  "00", 2))
              MyNumber = Trim(Left(MyNumber, DecimalPlace - 1))
          End If

          Count = 1
          Do While MyNumber <> ""
              Temp = GetHundreds(Right(MyNumber, 3))
              If Temp <> "" Then
                If Temp = "UN" And Count > 2 Then
                        Dollars = Temp & Left(place(Count), Len(place(Count)) - 3) _
                            & " " & Dollars
                Else
                        Dollars = Temp & place(Count) & Dollars
                End If
            End If
              If Len(MyNumber) > 3 Then
                  MyNumber = Left(MyNumber, Len(MyNumber) - 3)
              Else
                  MyNumber = ""
              End If
              Count = Count + 1
          Loop

          Select Case Dollars
              Case ""
                  Dollars = "Cero " & Mon
              Case "UN"
                  Dollars = "Un " & Left(Mon, Len(Mon) - 1)
              Case Else
                  If origNumLen > 6 And (origNum Mod 1000000) = 0 Then
                    Dollars = Dollars & " " & "de " & Mon
                  Else
                    Dollars = Dollars & " " & Mon
                  End If
          End Select

          Select Case Cents
              Case ""
                  Cents = " con cero centavos"
              Case "One"
                  Cents = " con un centavo"
              Case Else
                  Cents = " con " & Cents & " centavos"
          End Select

          LoTioHablaBolivares = UCase(Trim(Dollars & Cents))
      End Function



      '*******************************************
      ' Converts a number from 100-999 into text *
      '*******************************************

      Private Function GetHundreds(ByVal MyNumber)
          Dim Result As String

          If Val(MyNumber) = 0 Then Exit Function
          MyNumber = Right("000" & MyNumber, 3)

          ' Convert the hundreds place.
          If Mid(MyNumber, 1, 1) <> "0" Then
            If MyNumber = "100" Then
                Result = "cien "
            Else
            Select Case Mid(MyNumber, 1, 1)
                Case 1
                    Select Case Len(MyNumber)
                        Case 1
                            Result = "Un "
                        Case 3
                            Result = "Ciento "
                        Case 4
                            Result = ""
                        Case 6
                            Result = "Ciento "
                        Case 9
                            Result = "Ciento "
                    End Select
           
                Case 2
                    Result = "doscientos "
                Case 3
                    Result = "trescientos "
                Case 4
                    Result = "cuatrocientos "
                Case 5
                    Result = "quinientos "
                Case 6
                    Result = "seiscientos "
                Case 7
                    Result = "setecientos "
                Case 8
                    Result = "ochocientos "
                Case 9
                    Result = "novecientos "
            End Select
          End If
        End If
          ' Convert the tens and ones place.
          If Mid(MyNumber, 2, 1) <> "0" Then
              Result = Result & GetTens(Mid(MyNumber, 2))
          Else
              Result = Result & GetDigit(Mid(MyNumber, 3))
          End If

          GetHundreds = Result
      End Function



      '*********************************************
      ' Converts a number from 10 to 99 into text. *
      '*********************************************

     Private Function GetTens(TensText)
          Dim Result As String

          Result = ""           ' Null out the temporary function value.
          If Val(Left(TensText, 1)) = 1 Then   ' If value between 10-19...
              Select Case Val(TensText)
                  Case 10: Result = "Diez"
                  Case 11: Result = "Once"
                  Case 12: Result = "Doce"
                  Case 13: Result = "Trece"
                  Case 14: Result = "Catorce"
                  Case 15: Result = "Quince"
                  Case 16: Result = "Dieciseis"
                  Case 17: Result = "Diecisiete"
                  Case 18: Result = "Dieciocho"
                  Case 19: Result = "Diecinueve"
                  Case Else
              End Select
          Else                                 ' If value between 20-99...
              If Val(Right(TensText, 1)) = 0 Then
                Select Case Val(Left(TensText, 1))
                    Case 2: Result = "veinte"
                    Case 3: Result = "treinta"
                    Case 4: Result = "cuarenta"
                    Case 5: Result = "cincuenta"
                    Case 6: Result = "sesenta"
                    Case 7: Result = "setenta"
                    Case 8: Result = "ochenta"
                    Case 9: Result = "noventa"
                    Case Else
                End Select
              Else
                Select Case Val(Left(TensText, 1))
                    Case 2: Result = "veinti"
                    Case 3: Result = "treinta y "
                    Case 4: Result = "cuarenta y "
                    Case 5: Result = "cincuenta y "
                    Case 6: Result = "sesenta y "
                    Case 7: Result = "setenta y "
                    Case 8: Result = "ochenta y "
                    Case 9: Result = "noventa y "
                    Case Else
                End Select
              End If
              
              Result = Result & GetDigit _
                  (Right(TensText, 1))  ' Retrieve ones place.
          End If
          GetTens = Result
      End Function




      '*******************************************
      ' Converts a number from 1 to 9 into text. *
      '*******************************************

      Private Function GetDigit(Digit)
          Select Case Val(Digit)
              Case 1: GetDigit = "UNO"
              Case 2: GetDigit = "DOS"
              Case 3: GetDigit = "TRES"
              Case 4: GetDigit = "CUATRO"
              Case 5: GetDigit = "CINCO"
              Case 6: GetDigit = "SEIS"
              Case 7: GetDigit = "SIETE"
              Case 8: GetDigit = "OCHO"
              Case 9: GetDigit = "NUEVE"
              Case Else: GetDigit = ""
          End Select
      End Function
This function,s problems can be solved with the following formula referencing the cell where the result of the function is: 

="(BSF)    "&SI(LEFT(A1;10)="UNO MILLON";A1;IF(LEFT(A1;3)="UNO";IF(ISNUMBER(SEARCH("MIL";A1));MID(A1;SEARCH(" ";A1)+1;10^5);B1);B1))