As stated above, the convention pattern is to bank your OCT 2012 points before the end of this month ... then borrow your OCT 2013 points back into 2012 UY for Sept travel.
HOWEVER -- here is a different way to solve the problem:
* Bank you OCT 2012 points before the end of this month.
* Have points from a different UY transferred to you. (Rent a block of points to be transferred into your account from one of the
DVC Point brokers or a private party.)
* Book the SEPT reservation from the transferred points.
FWIW, I also have an OCT UY. We like visiting Aulani in Sept. I rented a block of FEB UY points through TTS that work perfectly for our summer/early fall travel plans and can still be banked into FEB 2014 by the end of Sept this year. Works great for me!