The range is enormous. If you ask a production house or an ad agency, they'll more than likely flip the question and ask you what your budget is. mhjohar's figures are a good starting point. Tell your boss, see whether he's okay or has a seizure. If he's okay, get in touch with a production house (not a solo freelance videographer please!) with a rough budget and a clear idea of what you want to accomplish. They should be able to advise you from there. Don't be afraid to shop around. It's not always the big names that will give you the best deal -- sometimes a young, hungry and creative startup will go the extra mile for you. (Cheaper is not necessarily better!)
PM me if you want a couple of contacts to get you started. There should be some in CS...