What if you added an auto-redirect after n seconds on the final page, such that it would redirect to some other page indicating that it had been displayed for that period of time. The redirect would be contained in the data file but only if it had been displayed for the full n seconds.
e.g.,
Code:
<head>
...head section stuff (Title, Description,etc.)...
<meta http-equiv="refresh" content="120;url=pagename.html">
</head>