It appears from your post that you intend to give priority for your CMA Final examination this June 2013 and clear it, and at the mean time contemplating to give your CS Executive examination too.
Firstly, you need to assess the level of preparation or knowledge you possess in both the courses based on the syllabus, as some of the subjects may be complementary.
Secondly, with close to two and half month to three months left for your examinations, evaluate your strength and weakness in both courses and take a call as to whether it is wise to appear in all the modules of both the examination or write single module.
Finally, be realistic and go with a positive mindset rather than going with half-hearted approach.
My suggestion would be to appear in both the examinations; since you are at final level of CMA and it is, probable that executive program at CS level may be relatively easier to crack, presuming that you possess good flair with theoretical knowledge too.
Best of Luck
Sathish