Sub DeleteUnusedMasterLayouts()

    Dim oDesign As Design

    Dim oMaster As Master

    Dim oCustomLayout As CustomLayout

    Dim i As Long

    Dim isUsed As Boolean

    'Loop through each design in the presentation

    For Each oDesign In ActivePresentation.Designs

        Set oMaster = oDesign.SlideMaster

        'Loop backward through custom layouts to avoid indexing issues when deleting

        For i = oMaster.CustomLayouts.Count To 1 Step -1

            Set oCustomLayout = oMaster.CustomLayouts(i)

            isUsed = False

            'Check if the custom layout is used by any slide

            For Each oSlide In ActivePresentation.Slides

                If oSlide.Layout = oCustomLayout Then

                    isUsed = True

                    Exit For

                End If

            Next oSlide

            'Delete if not used

            If Not isUsed Then

                oCustomLayout.Delete

            End If

        Next i

    Next oDesign

End Sub