I don't know what your office is quite like and what type of dress you normally wear, but I just picked up a pair of these from macy's:
http://www.macys.com/catalog/product...ognc?ID=192795
They are fairly light weight and I haven't had a problem yet with rubbing (granted I've only worn them twice and have a fairly short commute). They are light enough that you could wear tights underneath or just a pair of cycling briefs if you want. I liked the fact that there is a button up side, so you don't get chain grease on everything, works nicely.