You could use a T/F variable to track whether the user has watched the video.
- Create the T/F variable with a default value of False.
- On the slide with the video, add a trigger that adjusts the variable to True when the media (that is, the video) completes.
As needed, use trigger conditions that check the value of the variable to control other aspects of the course.
- For example, on the slide with the video, a trigger might change the NEXT button to Disabled when the timeline starts with the condition that the variable = False. The condition prevents the button from being disabled again if the user has already watched the video. So they could just move on from that slide.
It’s worth the effort to learn about variables and trigger conditions, because they provide the real power in Storyline. Here’s more info: