How to generate a random score in a textfield?

i really have a big problem on this part working on my project… my project is a videoke, that after the user sang the song he/she wants is that at the end, there is a score that will appear(random score from 80-100)… im just a NEWBIE who is seeking for your expert advise… :*( pls help dear brothers and sisters… thanx in advance=)