how to use opengl extensions

I want to use glColorTableEXT() so I included glext.h and tried to use the function in my code but I get an error when I compile saying that glColorTableEXT() is undefined. What do I need to do to get this function working? Thanks.

glColorTableEXT() is depricated, you can only use this extension on older graphics cards.

http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=2;t=016785

Greetz,

Nico