modifying menu links (wp_nav_menu ?)

I am trying to add a query string to the url of each menu element.

I found wp_nav_menu in the codex and tried

“link_after’ => ‘?q=something’ which added only to the link text and didn’t change the actual link.

Then I tried ‘after’ => ‘?q=something’ which sounded like it might work, but it didn’t seem to change anything.

Is there a way to do what I want? Is wp_nav_menu the right function?

To clarify, I want menu item links
href=”http://localhost/~wordpress/blogs/”
to become
href=”http://localhost/~wordpress/blogs/?q=something”