Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        If checkserial("12345-12345-12345-42345") Then
            MessageBox.Show("ok")
            'Hier der Code der ausgeführt werden soll wenn die serial ok ist
        Else
            'Hier wenn nicht
            MessageBox.Show("notok")
        End If
    End Sub
 
    Public Shared Function checkserial(ByVal seriennummer As String) As Boolean
        Dim serial(1), s As String
        Dim a(1) As String
        a(0) = "xxxxx-12345-1234x-12345"
        a(1) = "xxxxx-x2345-x1234-6543x"
 
        Dim c As Char
        Dim b As Boolean = False
        Dim i As Int16 = 0
        For Each s In a
            serial(0) = s
            serial(1) = seriennummer
            i = 0
            MessageBox.Show("1" & Chr(13) & serial(0) & Chr(13) & serial(1))
            For Each c In s
                If c = "x" Then
                    serial(1) = serial(1).Remove(i, 1)
                    i -= 1
                End If
                i += 1
            Next
            MessageBox.Show(serial(1) & Chr(13) & serial(0).Replace("x", ""))
            If serial(1) = serial(0).Replace("x", "") Then
                b = True
            End If
        Next
        Return b
    End Function