Hi manishkachhia I have already seen this and used it to achieve an accumulation of the value over 12 months, so:
Jan = Jan
Feb = Jan+Feb
Mar = Jan+Feb+Mar
The article was good for this, however my challenge I believe is slightly different in that against a month (eg. Apr-2013) I want to go and get the sum for the 12 months previous (eg. May-2012 to Apr-2013) and put this sum against the month of Apr-2013.