Maybe something like

=SUMPRODUCT(--(Qtr1!A2:A20B2-84),--(Qtr1!A2:A20<=B2),--(Qtr1!B2:B20))+
SUMPRODUCT(--(Qtr2!A2:A20B2-84),--(Qtr2!A2:A20<=B2),--(Qtr2!B2:B20))

--
HTH

Bob Phillips

(replace somewhere in email address with gmail if mailing direct)

"Throwme A Frigginbone"
wrote in message ...
I am trying to establish a 12 week rolling sum of cells on multiple
worksheets (1st qtr, 2nd, 3rd, & 4th) that will display on a Summary
worksheet. I am thinking this , On the Summary sheet I have a =today cell,
which will correspond to a column heading. I want it to calculate the past
12
weeks from the date "Today", which may span 2 worksheets.
My brain is not working right at the moment, so any ideas would be
appreciated. If more info is required, please reply and I will fill in the
blanks. Thanks!!