Executing php code from a Page

Ok why doesn’t this work? I am using WordPress 2.1 and all I want to do is execute this code: displayAmazonWishlist(”wishlist_id”); from a Page. It’s the code needed to get wp-amazon-wishlist working. Now I’ve tried both the new version of RunPHP and Exec-PHP. Neither will even execute the code and give an error. I don’t want to hard code the line because I need to have multiple pages with a different wishlist. What could be going wrong?