Public Class Form1
    Private myKlasse As Klasse
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        myKlasse = New Klasse()
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
        myKlasse.unload()
        myKlasse = Nothing
    End Sub
End Class

Imports System.Threading
 
Public Class Klasse
 
    Private timer As Timer
    Private callback As TimerCallback
 
    Public Sub New()
        callback = New TimerCallback(AddressOf Tick)
        timer = New Timer(callback, Nothing, 0, 500)
    End Sub
 
    Private Sub Tick(ByVal state As Object)
        Debug.Print(Date.Now.ToString("HH:mm:ss.fff"))
    End Sub
 
    Public Sub unload()
        timer.Dispose()
    End Sub
 
End Class