I found this softwarehttp://macfreedom.com/
It disables your internet connection for a predetermined time and it can only be restored by restarting. As I'm working with this thing on I'm realising just how often I feel the urge just to check my email, or have a look at my favourite sporting forum, or whatnot. Also it lets you keep your local network running so if you're running 2 or more networked computers for your samples you can still do that.
I've only been using it a few days but I can see it's going to help my productivity a great deal. But I may not have the in depth knowledge of why my footy team's season is down the toilet.
Cheers
Brett