Need a 12 month rolling value

I need a 12 month rolling number.

I need it to calculate a 12 period from the current date on the summary tab.

It can either go by the 12 months on the summary tab or by the 2012 and 2013 tabs and go by days.Attendance.xlsx

so if bob gets 2 points in January and 1 in july. Next January those 2 points will fall off and then he will be down to 1 point until july.

Here is a sample

Thanks

=SUM(OFFSET($J$4,,ROWS($J$4:J4)-1,1,12))

Would this work? I have it set up and it is calculating right but will this move next month so it stays accurate or will I have to adjust it again?