It is not uncommon for closing table adjustments. However, there are a lot of variables, laws, and circumstances that come into play. The biggest are the RESPA laws which as of a year ago greatly limited these kind of adjustments at closing. And, your lender may not allow an adjustment of that nature at the closing table also. Talk to your Realtor, Lender, and Atorney and see if between them all they can put together a strategy that might legally and ethically get you something.
Hope that helps.