I assume you are the administrator over your office LAN, the you can do this.
On the server computer (your computer)
1. Go to Control Panel\Administrative Tools
2. Open DNS, right click on Forward Lookup Zones and click New Zone.
3. Click next to pass the welcome screen of the wizard, then select primary zone.
4. Select "To all domain controllers".
5. Type facebook.com (without the www).
6. Select "Allow only secure dynamic updates".
7. Click Finish