How to use VBA to return a collection of PowerPoint Custom Layout objects when more than one is selected in Master view?

In PowerPoint, ActiveWindow.Selection.Type can return one of four types : None, Slides, Shapes or Text.

When in the Slide Master view and a single layout is selected in the thumbnail pane, the selection type returned is Slides and the following returns a Master object as expected:

Set obj = ActiveWindow.View.Slide

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But, when more than one custom layout is selected in the thumbnail pane, the following returns an error:

Set obj = ActiveWindow.Selection.SlideRange

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The error : "Selection (unknown member) : Invalid request. SlideRange cannot be constructed from a Master."

So my question is "how can I return a collection of custom layouts based on the current selection when the selection comprises more than one layout?"