I am trying to replace the helper that provides the compare box with the list of products added to it. My helper is going to get the product ids from a cookie instead of from Magentos session.

As I understand things I need to create a file in app/code/local/Mynamespace/Mymodule/Helper/Data.php and put my own class in this file. Is this correct or should I put the file somewhere else or perhaps give it a different name?