Office workout?

Are you allowed to sit on an exercise ball instead of your regular office chair? That would at least allow you to be working your core more than if you were just sitting in your regular, old office chair. Are you able to stand at your desk (for example, is your work station raised to allow you to sit or stand, or can it be modified)? Just getting up and standing while you're working will get your blood flowing and joints moving versus just sitting there all day long! I work with a headset at my desk, so I can sit or stand at my discretion. I do lunges, squats and reverse leg raises while I'm working. I have co-workers who have brought small free weights and they do some upper body exercises while working at their computers. I also make a point of getting outside and walking for a minimum of five minutes at least one time per day. I usually walk for 20 minutes during my lunch break (and I only get a 30 minute lunch break). I have the benefit of being able to eat at my desk, which is great because then I can walk during my actual lunch break instead. We have to fit it fitness where we can!