'coded by loyalty
'http://loyaltyHF.blogspot.com
Private Function ValidateLuhnAlgo(ByVal combo As String) As Boolean
  Dim sc = 0
  If IsNumeric(combo) Then
    combo = StrReverse(combo)
    For i = 1 To combo.Length
    If i Mod 2 = 0 Then
    If Val(combo(i - 1)) * 2 > 9 Then
    sc += Val((Val(combo(i - 1)) * 2).ToString()(0))
    sc += Val((Val(combo(i - 1)) * 2).ToString()(1))
    Else
    sc += Val(combo(i - 1)) * 2
    End If
    Else
    sc += Val(combo(i - 1))
    End If
    Next
    If sc Mod 10 = 0 Then Return True
  End If
  Return False
End Function