Declare Function SetWindowPos Lib "user32.dll" (ByVal hwnd As IntPtr, ByVal _
      hWndInsertAfter As Int32, _
    ByVal x As Int32, ByVal y As Int32, ByVal cx As Int32, _
    ByVal cy As Int32, ByVal wFlags As Int32) As Int32
 
    Const SWP_NOSIZE As Int32 = &H1
    Const SWP_NOMOVE As Int32 = &H2
    Const SWP_NOZORDER As Int32 = &H4
    Const SWP_NOACTIVATE As Int32 = &H10
    Const SWP_DRAWFRAME As Int32 = &H20
    Const SWP_SHOWWINDOW As Int32 = &H40
    Const SWP_HIDEWINDOW As Int32 = &H80
    Const HWND_TOPMOST As Int32 = -1 'bringt ein fenster an die oberste stelle
    Const HWND_NOTOPMOST As Int32 = -2 'bringt ein fenster an die unterste 
    ' stelle eines containers
    Const HWND_BOTTOM As Int32 = 1 'bringt ein fenster an die unterste position 
    ' aller fenster
 
    Private Sub frmMain_GotFocus(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles Me.GotFocus
           SetWindowPos(Me.Handle, HWND_BOTTOM, 0, 0, 0, 0, SWP_NOMOVE Or _
           SWP_NOSIZE)
    End Sub

    Private Sub frmMain_GotFocus(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles Me.GotFocus
        If frmHauptform.chkOnTopVordergrund.Checked = False Then
            SetWindowPos(Me.Handle, HWND_BOTTOM, 0, 0, 0, 0, SWP_NOMOVE Or _
              SWP_NOSIZE)
            Else
            SetWindowPos(Me.Handle, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE Or _
              SWP_NOSIZE)
        End If
    End Sub

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Programmieren ist heute ein Wettrennen zwischen Programmierern, die versuchen bessere und idiotensicherere Programme zu entwickeln und dem Universum, dass versucht bessere Idioten zu entwickeln