Public Class Form1
[...]
    Protected Overrides Sub WndProc(ByRef m As Message)
        If ((m.Msg = WM_NCLBUTTONDOWN AndAlso _
             m.WParam.ToInt32() = &H3) OrElse _
             m.Msg = WM_NCRBUTTONDOWN) Then
            Return
        End If
        MyBase.WndProc(m)
    End Sub
    Private Const WM_NCRBUTTONDOWN As Integer = &HA4
    Private Const WM_NCLBUTTONDOWN As Integer = &HA1
End Class