Some ideas for hiding Promo Codes

[AndromedaKerova]

I'm curious how I would alter the message. I want it to appear like this:

Congratulations!
You've discovered the Promo Code for the: Konamibunny

Code: PROMOCODEHERE

Enter it on the Promo Code page: http://chibifurs.elementfx.com/promo

It would be awesome if it played a defined sound as the box pops up too.
If possible, what format would the sound need to be in and how long?

Is it also possible to alter the code so only members can enter the code and not a guest or nonlogged user?