Check when certain frames are hit?

Hi have a site and in this site I have a page that has three buttons. Each button take you to a series of 2 to 5 pages. When you are done with one section it takes you back to the page with the 3 buttons.

What I would like to have happen is to have the user be force to go through each one of the 3 sections, and then be returned to back to the page with the three buttons, but after they have visited all 3, a fourth button would then become visible so that they could move on. But only if all 3 sections had been visited first.

How can I have it check to make sure that the 3 sections have been visited?

Please help.