PowerPoint New Window
Well, after exhaustive effort and nobody being able to offer any advise, I discovered that it can't be done!
However - if you the page you link to uses a browser history call for its close or hyperlink, you can return to the PowerPoint at the slide where you left off.
Here's what I did - for the related practice tests - I changed the "Show All Questions" Button to "Return to the Lesson" and used onclick="history.go(-1)" as the hyperlink. For the Millionaire, I used onclick="history.go(-18)". The result can be seen by viewing the following lesson - Measurement Ladders.