Hi sildawg,
First off, a 680 is fantastic GMAT score (it's just shy of the 90th percentile overall), so you should apply to any Business Schools that interest you. GMAC has publicly stated that the Official Score that you earn on Test Day is within +-30 points of actual ability, so your 680 could have easily been a 710. This is all meant to say that the difference in performances is marginal (and Business Schools know that). That all having been said, the answer to your immediate question is YES - you could score 700+ in less than two weeks.
The next set of important questions have to do with how you took your last few CATs:
1) Did you take the ENTIRE CAT each time (including the Essay and IR sections)?
2) Did you take them at home?
3) Did you take them at the same time of day as your Official GMAT?
4) Did you ever do ANYTHING during your CATs that you couldn't do on Test Day (pause the CAT, skip sections, take longer breaks etc.)?
5) Did you ever take a CAT more than once?
Since you're interested in Finance programs, a higher Quant Scaled Score would definitely be helpful. A Q42 is not going to impress anyone - so if you do plan to retest, then focusing your practice on that area of the Exam would be a good idea.
GMAT assassins aren't born, they're made,
Rich