Well, for starters you're not going to be able to 'hide' query string values because they appear in the presentation of the URL and there's really no way around that.
What you can do however, is find an alternative method of passing the values from page to page. Possible methods include passing the values within a cookie or some other codeable process.
Even if you had a method to obscure the URL being called it's still going to show the query string. Even if you find a way to obscure the query string in some browsers it won't necessarily work in all browsers :) If you truly don't want users to see the values passed then use a more invisible method to pass them (but there will always be ways to see them if the users REALLY want to).
On the other hand, if the values being passed are formatted in such a way as to make no sense to the end user but make perfect sense to your programming then what's the harm if they see them.