Frederic Baumann has produced two brilliant Vegas Pro Plug Ins for correcting White Balance and dealing with underexposed images. Details are on his web site at:-
FBmn Software - plugins for Sony Vegas Pro 10
along with examples of the two Plug Ins in operation. They are both excellent and well worth having in your armoury.
You can download either or both on a trial basis if you want to try them out before buying --- and their cost is not at all unreasonable.
Hope this is of some help.