Controlling access to content

I have a title that I am playing with that consists of a series of pages (listed in the table of contents) on each page is a video. Each video builds on the previous video. So, I want to ensure two things:

1. Users do not move on to the next page before the video is finished, and
2. Users do not "skip ahead" several videos through use of the table of contents.

What is the easiest manner in which to do this?

For the first part I've thought of associating an action that requires video completion before the next button is visible.

This second part has me puzzled.

Thanks for any feed back

Dave