Hide a button

Hello,

I have 3 entities, Account, Registration and Event.

I have a button that register the $currentUser for the event he/she has selected in a templategrid. I have a working validation so that a user cannot register for the same event more than once.

But, after a registration the button stays in screen with the same text 'Register!', the user will get an error that says 'already registered' if he/she presses the button.

I would like to just hide the button after a registration and put the text; You have registered for this event.

How can this be done?

Thanks,

Joey