Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Dim TestThread As New Threading.Thread(AddressOf fThread)
        TestThread.Start()
    End Sub
 
    Sub fThread()
        setText("test")
    End Sub
 
    Private Delegate Sub dWriteText(ByVal text As String)
 
    Public Sub setText(ByVal text As String)
        If Me.TextBox1.InvokeRequired Then
            Me.TextBox1.Invoke(New dWriteText(AddressOf setText), _
              New Object() {text})
        Else
            Me.TextBox1.Text = text
            Me.TextBox1.Refresh()
        End If
    End Sub