Life Hacking

The Lifehacker website aims to help us become more productive. Just what I need, so I had a look, and ended up installing a Greasemonkey script on Firefox that blocks access to Fitzrovian, personal webmail etc. during office hours (of course, I did all of this during office hours, too). Trouble is, you can turn off greasemonkey with one click (e.g. at lunchtime, as I write this), but it discourages me from idle surfing. Can anyone tell me how to rewrite the script so that it blocks access all morning, then lets me in over lunch, then blocks again in the afternoon?

Of course, all of this might just be a new form of procrastination. Apparently O'Reilly or someone commissioned them to do a book on life hacking, but then cancelled it because they kept missing their deadlines...