Actually you could make this so you can compare ANY office to the total.
Create a calc (or a series of calcs, depending on how the data is set up.)
IF [Office] = [User-selected-Office-Parameter] then [ (whatever measure) ] END
So you'd set up a param that lets the user select an office. Then you would save in the calc (or series of calcs if you need to save a series of measures) the values for that office. (for all the other offices, the calc value would be null.)
SUM([ office calc]) would give you the data for that one office. SUM([original measure]) would give you the entire organization (assuming you don't filter out other stuff on the sheet.)
I'm so sorry. I thought I replied months ago to this. This was great. Thank you very much.