[gazhayes]

In your case it seems fairly simple at first glance.

You should delete all the standard contexts and make:

Office
Mac
Bobby
Jane
Frank

(the last 3 being examples of staff names).

However, I would say that you may not have understood the complete idea behind GTD and when you read the book you will probably come up with more contexts e.g. I'm sure you do have a life outside of work and you probably do things like eat (maybe you need some specific groceries while your at the store), perhaps even have a spouse, maintain semi-regular visits to the dentist etc. GTD is how you live, not just work.