I would like to be able to block work staff from accessing their personal facebook accounts BUT would like them to be able to retain the ability to access our own company facebook page. Is this possible?
You could setup the web blocker to man in the middle your employees facebook so you could get past the ssl and use a block based on url. However, that would require alot of work and may get your employees upset.
A better system is to not allow facebook and just allow the people who need it access. Chances are only a few people in your PR department actually need facebook access and the rest of the company would be fine without it. I do not know how your web blocker is setup, but blocking based on computer or who is logged in is the best method.
This method is not as powerful as blocking most of facebook, but it is more realistic.