If you can detect in an event when a video ends, you could just do:
on video finished playing:
add 1 to position
call "run" ()
If you have no indicator when a video finishes, but the user also has no control over the video, you could start a timer with the length of the video + some small leeway, and on this timer, you do the same actions above.
If you want the user to be able to skip the video, ofc you need to add that functionality, too (on left click and video running -> stop video, position +1, run, something likw that)