I can't think of a reason why you might want to perform such a task, please enlighten me.
If you are applying a random unique number for some tagging reason then I'd just add a Yes/No field to each record so you can say whether you want to include it a queries results which you can then employ for some alterior motive
Alternatively, I would consider either using an RND function with a 200,000,000,000 but I've heard the RND isn't assured to be random.
Seems an odd objective mind..
Ian