restrict a bookmarklet that opens a random link on page

I found this bookmarklet that opens a random link on your current page.

javascript:void(window.open(document.links[Math.floor(Math.random()*document.links.length)].href,'_self'));

I wanted to use this on a website, but I also wanted to restrict it so certain links wouldn't be opened. Is there a way I can do this?

(also I found the bookmarklet here)