CheckPartitaIva

Public Sub CheckPartitaIva(Numero As String) As Boolean
  Dim i As Integer
  Dim A As Integer
  Dim B As Integer
  Dim C As Integer
  Dim tmp As Integer
  Numero = Trim(Numero)
  If Len(Numero) <> 11 Then Return False
  For i = 1 To Len(numero)
    If Mid(numero, i, 1) Not Like "[0123456789]" Then
      Return False
    Endif
  Next

  For i = 2 To Len(numero) Step 2
    tmp = CInt(Mid(numero, i, 1)) * 2
    If tmp > 9 Then tmp -= 9
    A += tmp
  Next

  For i = 1 To Len(numero) Step 2
    tmp = CInt(Mid(numero, i, 1))
    B += tmp
  Next

  C = A + B
  Return C Mod 10 = 0


End