You would have to implement custom JavaScript to accomplish this. You would use YouTube's iframe API, and check for the video's state (not played, playing, finished):
https://developers.google.com/youtube/iframe_api_reference
When the player reaches the desired state, you can redirect the page:
http://stackoverflow.com/questions/503093/how-can-i-make-a-redirect-page-in-jquery-javascript
Do you have the technical resources to accomplish this?