I don't know if you have administrative rights on your computer at work. If you do not, then you may not be able to install any programs.

If you can install programs, then maybe one of these will help:
http://internet-filter-review.toptenreviews.com/

Parental controls. If your computer at work is on Vista or windows 7, parental controls are already there...but, again, only if you have administrative rights to your computer... I believe--I could be wrong.

If you can enable parental controls, whether built into the operating system or from an internet filter program, to block sites you seem to be addicted to visiting, try this.

Go to this site to get a password:
https://www.grc.com/passwords.htm

You'll have to enter the password twice, the second time for confirmation. Select the first five or so characters of your "perfect password" and paste into both password boxes.

Do not write down your password. This is cool because if you visit the perfect password site again, you will not get the same password.

Voila, you should never be able to bypass your parental controls.

Another thing that occurred to me is to have a friend at work make up a password for parental controls and promise to never tell you what it is.

You will have to be careful about what sites you add to the blocked-site list as it might ask for your password again. So you might want to start with a memorable password for the parental controls first just to create a list of blocked sites, but then change the parental controls password as per the instructions above to make it an un-memorable password.

edit: I feel obliged to say that if you set up which sites are blocked in a bad way, you might brick your computer (meaning making it unusable). That would be very bad of course as you'd have to explain to the IT guys why they have to re-install the operating system and programs. So be careful about your parental controls as you don't want to cripple all of the internet activity.