OK

Find the image (try here)

I would insert it on the large slide master of the last presentation OR on the last slide

Open the last presentation (work on a COPPY!) and press ALT + f11. The vb editor should open

INSERT > Module (make sure you are using the INSERT menu in the editor not the normal insert)

Copy the code below and paste it into the editor

Sub chexClose()
If MsgBox("Do you want to quit?", vbYesNo, "Quit?") = vbYes Then
While SlideShowWindows.Count > 0
SlideShowWindows(1).View.Exit
Wend
End If
End Sub

Now go back to normal edit mode and select the red x. INSERT > Action and choose Run Macro.

Note this will only run the macro in show mode.

Save the last presentation as a macro enable presentation .pptm

TEST

If you get stuck try this as your last presentation

DOWNLOAD DEMO