[Flash 8] Enable/disable links based on progress

I am trying to figure out the best approach to making certain links unavailable until a certain chapter of a flash presentation is completed.

I other words, if a movie is broken up into chapters. The veiwer needs to complete ‘Chapter 1’ in order to be able to move on to ‘Chapter 2’. There will be a ‘Table of Contents’ page with the Chapters listed. What I need to be able to do is gray out the links to the Chapters that have not been completed. Once the user completes a Chapter and they decide to return to the ‘Table of Contents’ page. All of the completed chapters will be available for later reference.

I need to be able to do all of this using Actionscript and possibly PHP to store the users progress into a database, for later reference. This project is going to be a tutorial type presentation using the PageFlip flash book.

If anyone has an example or is willing to give me some ideas, your help will be much appreciated.

Thank you.