The sort parameter should come from the URL that the user goes to when they click on a link. This should work the same for you with a list, but you should use a jump menu instead. This type of menu will take you to the page specified with the URL parameters that you use in the link.
This way when the user makes a selection the page is reloaded with the corresponding sort parameter. As for the error you are getting have you tried it the way it shoes in the Solution Recipe? I think it will be best to get it working like this first before you try to use the menu. Let me know if you get this error when doing it just like the Solution Recipe and I can get a ticket opened for you on this issue.