Detecting first visit in multiple swf website

hello wonderful people
i am making a website that has several main swf files that navigate to each other via links (nobody’s loading anybody). all of them have external preloaders.
i have a nice intro, about a minute long at the start of the homepage.

what i need to do is make the intro play only on the first entry to the site, and not when you reach it from the site’s other pages. it’s about either detecting first entry, or making the other pages pass a variable to the homepage. but i dont have the slightest idea how to do it…

because they have no physical connection, communication between them, i think it should be something like opening and changing a text file each time you enter a page, that the other pages would read. and this works for one user, but how to make it work for 60+ users at once?

and if you need some ip logging program written in some other language (i dont know any other) that creates unique values for each user, how to tell flash to read a specific file it creates? somehow based on the ip of the system the swf is played at?

if anybody can help me please
lots of thank you s and everything
michael