Assuming that your first date (1-1-07) is in row 2, then in C2 put this formula
=SUMIF($A$2:A2,">" & A2-365,B$2:B2)
as you fill that formula on down the sheet, it will automatically do the
rolling-total for all dates that are within the past 365 days (actually may
be 364, but testing can confirm it for you - if 365, then change 365 in the
formula to 366). You won't have to change the formula, it fills down very
nicely.