Years ago we built in DNN 5x a video training course website system where we had all of the tables and management of permissions/tracking done through XMod Pro + DNN as our application development platform.
In that solution we'd put together there was
- a library and series/order of videos to be watched
- each user could watch the next one and previous ones but could not start a new video until they'd watched to the X minute mark of the previous video
- they were given a time range to watch and continue
- they were tracked on how many times they watched each
the video security was managed through windows media streaming server and sql server at the time but we've since done the same type of protection/security through Amazon S3, cloud front and dynamic urls...
DNN is a great platform to use for building something like this because it takes care of all the users, roles, permissions, store system if you want, etc and you then build the custom functionality with custom modules, or for us, through XMod Pro.
Let me know if you're still looking at how to accomplish this and I can help outline how I would recommend doing it with a few specific tools/modules.
Oh, though, too, to one of the other comments/posts, it's not a cheap idea to throw together overnight. That project was a 40K project several years back...