Public Class Main
    Public Tests As New Test
    Private ListenerClass As New Listener
 
    Private Sub main_Load([...]) Handles MyBase.Load
        ListenerClass.StartListener
    End Sub
End Class
 
Public Class Listener
    Private ListenThread As Thread
 
    Public Sub StartListener()
        ListenThread = New Thread(AddressOf Listen)
        ListenThread.Start()
    End Sub
 
    Private Sub Listen()
    Received()
    End Sub
 
    Private Sub Received()
            Tests.CancelBW()
            Dim txt As String = Tests.Label
            txt = txt.Replace("%TEST%", CStr(Packet.Test))
            Tests.Label = txt
            Tests.StartBW()
    End Sub
End Class
 
Public Class Test
    Inherits Label
 
    Private TestBW As BackgroundWorker
    Private TestLabel As String
 
    Public Sub New()
        TestBW = New BackgroundWorker()
        TestBW.WorkerReportsProgress = True
        TestBW.WorkerSupportsCancellation = True
        AddHandler TestBW.DoWork, AddressOf DoWork_TestBW
        AddHandler TestBW.ProgressChanged, AddressOf ProgressChanged_TestBW
    End Sub
 
    Public Property Label() As String
        Get
            Return TestLabel 
        End Get
        Set(ByVal value As String)
            TestLabel  = value
        End Set
    End Property
 
    Public Sub StartBW()
        TestBW.RunWorkerAsync()
    End Sub
 
    Public Sub CancelBW()
        TestBW.CancelAsync()
    End Sub
 
    Private Sub DoWork_TestBW([...])
        If TestBW.CancellationPending = False Then
            TestBW.ReportProgress(100)
        Else : e.Cancel = True 'ByVal e As DoWorkEventArgs
        End If
    End Sub
 
    Private Sub ProgressChanged_TestBW([...])
        Me.Text = Me.Label 'Hier tritt der Fehler auf
    End Sub
End Class