I'm looking to add a block to the top of the register.php page... I need users to input usernames in a specific format and being able to add a block to the top of the page would likely do the trick...

Has anyone done this before? Is there an EASY way to do it?

But how can I set the block to only be visable in the registration page? I don't have that option when I create the block... I can choose individual modules or ALL PAGES, but not the registration page exclusively, which is what I'm looking for...

If I'm misunderstanding forgive me... but simply setting it to unregistered users isn't really the issue... it's limiting the block to the registration page only that I'm trying to accomplish...

Thanks for helping out... any more ideas?

I would first try to edit the language file and see if that will help you. Look in languages/english/user.php

This looks like the language file that sets the wording for the registration page. Edit the text from just "username" to " enter your username in the this specific format".

I would try that first. If that doesn't work for you, I would then edit the register.php file to add your content. I am not sure how proficient you are with php, but I would not start plugging stuff into that file without some confidence you know what you are doing.