so you are trying to create what is called a many to many relationship.
you need to use three tables for this,
*users
*videos
*uservideos
users:
userID - Primary Key
userName
etc....
videos:
videoID - Primary key
videoNmae
etc....
uservideos:
uservideoID - Primary Key
uservideoUserID - creates relationship to the users.userID
uservideoVideoID - creates relationship to vides.videoID
for assigning video to the user, you would need to use the data assist manage relational table behavior.
for displaying videos that relate to the user, you would need to use a joined sql query.
Andrew Reed posted a good thread on using the Manage relational table behavior here:
showpost.php?p=84393&postcount=17
and you can find more details on using join queries here:
sql_join.asp