Public Class MyCheckBox
    Inherits System.Windows.Forms.CheckBox
    Private Const WM_LBUTTONDOWN As Integer = &H201
    Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
        If Me.[ReadOnly] AndAlso m.Msg = WM_LBUTTONDOWN Then Return
        MyBase.WndProc(m)
    End Sub
    Public [ReadOnly] As Boolean 
End Class