Just Use a Keyword Rated 1 out of 5 stars

You don't need this.
Simply create a keyword like 'goback'
with the url:
http://web.archive.org/web/*/%s

Then just type goback followed by a space and the domain for the site you want.
example: goback yahoo

This will bring up the Wayback machines archive of the site, you can then add the rest of the path for specific page in the native Wayback search form at the top of the page.