Widget "▶Listings" Display in Random Order?

Hello everybody

I added the Widget “▶Listings” which displays a custom list of website listings. It is supposed to show my Featured Listings and I would like to have them in a random order. I tried to edit the query string but it didn’t work.
For a the front page slider it worked by simply adding “&orderby_rand” to the query string. However, for this widget it does not.

Any ideas? 🙂

The Query String:

meta_key=frontpage&meta_value=yes&post_type=listing_type
&posts_per_page=10