<DllImport("user32.dll", SetLastError:=True)> _
Private Shared Function SetWindowPos(ByVal hWnd As IntPtr, _
    ByVal hWndInsertAfter As IntPtr, ByVal X As Integer, _
    ByVal Y As Integer, ByVal cx As Integer, ByVal cy As _
    Integer, ByVal uFlags As UInt32) As Boolean
End Function

ReadOnly HWND_BOTTOM As New IntPtr(1)
ReadOnly HWND_TOP As New IntPtr(0)

Private Const SWP_NOSIZE As UInt32 = &H1
Private Const SWP_NOMOVE As UInt32 = &H2

Private Sub btnSendToBottom_Click(ByVal sender As _
    System.Object, ByVal e As System.EventArgs) Handles _
    btnSendToBottom.Click
    Dim flags As UInt32 = SWP_NOMOVE Or SWP_NOSIZE
    SetWindowPos(Me.Handle, HWND_BOTTOM, 0, 0, 0, 0, flags)
End Sub

Private Sub btnBringToTop_Click(ByVal sender As _
    System.Object, ByVal e As System.EventArgs) Handles _
    btnBringToTop.Click
    Dim flags As UInt32 = SWP_NOMOVE Or SWP_NOSIZE
    SetWindowPos(Me.Handle, HWND_TOP, 0, 0, 0, 0, flags)
End Sub