CS in addition to MBA finance will help you in dealing with various financial matters of organization including corporate restructuring. Acknowledge that a CS course will take at least 3 years to complete after graduation or post graduation. If you would have already a CS then I would have recommended you to go for MBA finance. But as per my opinion, CS after completing MBA looks time consuming. However, if you want to pursue it side by side by your job, then it seems to be a better option.