Flash on the top page to play only the first visit in a session

I have a small Flash movie contained in my home page that I would like to be played only when the user lands the first time (all subsequent landings will display a static image) …so if the user hits the back button they will see the image NOT the animation. or if the user hits the home button in the site, they will see the image NOT the animation. If the user leaves the site and comes back, I would like to show the animation again.

Do I need to use a cookie or something? Please help,

A cookie or session variable will be required and you will have to change the HTML rather than the Flash movie.

If you were to do it in ASP, this would do the job:

if request.cookie("visited") = "" then 
  response.cookie("visited") = "true"
  response.cookie("visited").expire = date() + 90
  ' insert flash movie
  ' insert img
end if

I have something like that but I am working with Joomla and php.
Can you help me in what direction I should go?
I don’t have too much experience in coding, but I can tweek things to make them work. if anybody interested ? Here is my website with the problem.