What am I missing in my AppController.h file ? (I followed a scrolling text tutorial)

Hi, I'm trying to create scrolling text in my about window. I follow this tuorial : http://cocoadevcentral.com/articles/000044.php . The code compiles fine but I think I'm missing something in my AppController.h file. I included my project in an attachment

Any help would be greatly appreciated. Thanks in advance.

Attachment: AboutBox.zip (60.0KB)