Public Class Form1
 
    Private WithEvents t As New Timer
    Private Event port_switched(ByVal port As Integer)
 
    Private io_15 As Boolean = False
    Private counter As Integer = 0
 
    Private Sub Form1_FormClosed(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
        Debug.Print(counter.ToString)
        'hier kannst du dann im direktfenster sehen, wie oft form_closing 
        ' abgearbeitet wurde
        Stop
    End Sub
 
    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        counter += 1
    End Sub
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        t.Interval = 2000
        t.Start()
    End Sub
 
    Private Sub t_Tick(ByVal sender As Object, ByVal e As System.EventArgs) _
      Handles t.Tick
        If io_15 = True Then
            RaiseEvent port_switched(15)
        End If
    End Sub
 
    Private Sub ports(ByVal msg As Integer) Handles Me.port_switched
        Me.Close()
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        io_15 = True
    End Sub
End Class