Hi Omar, in order to practice your timing, I would suggest you to buy ETS paper tests at http://www.mba.com
. They are of absolutely good quality. You will download those pdf PT at the cost of ~25$ for 3 paper tests and there are 9 of them. Print them out and practice them by timing yourself with a stopwatch. I'm suggesting this since you cannot practice CATS at home... Of course, the best thing is to practice on CATS or else, try to join the GMAT challenges which require only 1h15min of silence. The next one is in 2 weeks and I believe that you should at least try a few (GMAT challenges/Kaplan
CD/PR CD) before your next attempt. But to answer your original question, YES it is possible to increase your score from 640 to 700+ within 1 month. Good luck.