How do I limit audio to play just once on first visits to slide?

Ok I got it to work with a little help from information from Articulatebrian's Screenr sample.

Here is the link for anyone interested...

https://player.vimeo.com/video/145579332

It is pretty much what you described but it was very helpful to have the samples on the video of exactly how the variables are set up.

Also most important for my use was that I had to duplicate each of the audio play variables ( I called them "playonce") on each slide that I had audio that I want to stop if the user returns there.  Another main difference  that I changes was that I changed the "set the audio to true" variable to NOT be when the media completes, but at the start of a timeline of a button (Variable Trigger button).  This button would normally be off screen.

I did this because I don't want the user to have to wait for the audio file to complete if he chooses to be impatient and go on to his chosen slide.

So what happens on each slide is the audio starts to play, then in a second the Variable Trigger button sets the "playonce" variable to true. 

I also included a button for the user to click if he changes his mind and wants to play the audio on the slide again.  This was part of my objective.  I have included a sample attached file.