You can submit videos in parts as long as it is clear the run continues from one part to the next (e.g., by keeping your cue and balls on the table). You might want to set a timer so you can deliberately stop and restart recording to help make it more clear the run is continuous from one video part to the next.
FYI, here's a quote from the BU Exam Challenge rules that might be helpful:
Your submitted video must be a continuous, uninterrupted, and unedited run at the entire Exam, and it must be obvious there is no trickery or cheating involved. During the entire video, stay in the frame of the camera (unless you absolutely need to take a bathroom break), keep balls on the table during each drill (e.g., pulling them out in groups of 4, 5, 8, or 10 during Exam I), and keep your cue on or against the table when spotting balls and between drills. You are not allowed to practice shots in between each of the required drills or shots. If you need to break up your video into multiple parts to store or upload them separately, make sure it is totally obvious that the run is being continued without interruption (e.g., by pausing in the middle of a drill with all of the balls and your cue remaining on the table). If you are having trouble with your video file sizes being too large, you can dramatically compress them using a free software tool called HandBrake.
Good luck in the Challenges,
Okay but more often than not, I will be focused on the playing then I hear a beep which means the camera stopped recording, meanwhile at this second when the video stopped the cue is in my hand maybe chalking or something.
So you mean after this I put the cue on the table then start recording?