hi i am trying to get this code

http://www.andrewpeace.com/javascrip...ng-screen.html

to run just on the products pages, i can get the code running across the whole site but not just on the products pages.

i've created a .js file (without script tags) and put it in the product_info folder and now im really stuck and dont know which files to edit , any help would be very much appreciated thank you