postponing start date of period

hi all, i am a new memeber . i liked this site so i joined. i'm hoping some one can give me ans to my questions.
i'm a 29 yr married woman livin in us.i'm visiting india on aug 20 n i'm goin with my husband n he can stay only 4r 3 weeks n i have planned on visiting a few temples while he's there in india.i want to postpone my periods 2 a convenient date using my 21 day combination birth control pill( femilon,i bought it 4rm india)right now i'm not using any pills.i had my period on aug 6.i want to postpone it to sep 17.i dont wanna take 2 packets without break.i want to know if i can start takin the pill 4rm 28 aug so that i'll finish the pack on sep 17.my problem is i'm not sure if it'll be effective if i start takin pills 4rm 28 aug ( that will be 23 days after my period). i'm really confused.pls someone with a good knowledge help me.i want to be 100% worry free n dont want to take any chances.
thank you ladies,have a good day.
yamika