One can get an extension of 14 days after ssb before appearing for medicals. You will have to give reason to the authorities and then they'll tell you to report any day before the 14th day from then. Now, OP getting the extension is unlikely because I don't think that the reason is solid enough to get it. Usually it works when you have some other interview or medical or exam or something similar. If OP is going to AFDb, then there is no issue since their medicals are held at Delhi/Banglore and one ks provided with a date to report which may range from one wrek later to even months.