Notify for One Site Only (reverse whitelist)

Is there a way to modify this code so that visitors receive a notification when they are leaving the site to visit just ONE other website?
a[href*=”//”]:not([href*=”yourwordpressinstallation.url”])

Let’s say I only want people to get a warning when they’re leaving my site to visit Google.com. I tried simply omitting the word “not” and including “google.com” in place of the URL, but that didn’t work.