Restricted navigation with seekbar

What I want...
User is not able to advance without viewing slide in entirety including all audio. User can go backwards to review slides previously viewed and then come forward to point where they left off. Customer wants seekbar for each slide.

Problem: With locked setting it appears that users cannot review previously viewed slides. With restricted setting, users can see previously viewed slides, but can also move seekbar ahead without viewing all content on a slide previously unviewed.

How do I set the seekbar so it cannot be advanced on a unviewed slide? I have searched all the 'how-tos' and threads. Thanks.