How can one control the start/stop/close actions of PowerPoint presentations from Excel or from another presentation?

This is a follow-on question from: Using PowerPoint VBA to assign [Alt-Tab] to an action button

I am trying to use VBA in Excel to control PowerPoint presentations.  The below code was provided by Jamie Garroch in response to a similar question.  The procedure [StartSlideShow] works to open a presentation in Slide Show mode, but the procedure [ExitSlideShow] is not available to run as a macro.

Option Explicit

' Macros for opening a presentation, starting and stopping a slide show
' Runs from any VBE, including Excel (uses late binding)

' Define late bound objects for PowerPoint application instance and presentation
Public appPPT As Object
Public objPres As Object

' Start a slide show
' Set FilePathAndName to the presentation file to be opened
' Assign macro to relevant action button
Public Sub StartSlideShow()
  Dim FilePathAndName As String
  FilePathAndName = "c:\temp\test.pptx"
  ' Create an instance of PowerPoint
  Set appPPT = CreateObject("PowerPoint.Application")
  ' Open the PowerPoint file specified by the string variable FilePathAndName
  Set objPres = appPPT.Presentations.Open(FilePathAndName, ReadOnly:=msoFalse, Untitled:=msoFalse, WithWindow:=msoFalse)
  ' Run the slide show
  objPres.SlideShowSettings.Run
End Sub

' Exit the specified Slide Show or the first one if none specified
' Assign macro to relevant action button
Public Sub ExitSlideShow(Optional objSSW As Object)
  If objSSW Is Nothing Then
    appPPT.SlideShowWindows(1).View.exit
  Else
    objSSW.View.exit
  End If
End Sub

' Tidy Up (run when closing Excel VBA project)
Public Sub Tidy()
  Set objPres = Nothing
  Set appPPT = Nothing
End Sub

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If I change the [ExitSlideShow] procedure from the above code to the following then it works, but I believe it is now just closing the first presentation, instead of closing the file specified in [StartSlideShow], and this won't work, because I will be opening multiple presentations at a time.

' Exit the specified Slide Show or the first one if none specified
' Assign macro to relevant action button
Public Sub ExitSlideShow()
  appPPT.SlideShowWindows(1).View.Exit
End Sub

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