Button for unprivileged users

Hi all,
I’ve started using RT some days ago and I’m very happy of it!
I’m just trying to adapt it to our company policies…
One stuff that our manager wants is the possibility for the unprivileged user
that looks on web his ticket status the possibility to press a button and
increase the priority of the ticket.
Is it possible to create this button working on some callbacks? Could you give
me some useful information on how to do that?

Thank you a lot