download
www.linkex.dk
place it on any of your domains
put your site url that they are supposed to be linking to in the "Link Settings" - "Alternative Backlinks" box
while logged in, add their site that is supposed to have your link to your linkex.
run the verification script.
that's a good way to use linkex as a secondary link verification script without using it on any of your pages. (not that's there is anything wrong with using it)
~Ray