Hi Amy.

Am Mon, 9 Jun 2014 13:50:09 -0700 (PDT) schrieb Amy:

=SUM(OFFSET(B3,COUNTA(B:B)-30,):OFFSET(B3,COUNTA(B:B),))

Your dates in column A, the values to sum in column B

If I understand you correctly then try:
=SUMIFS(B:B,A:A,"="&(A3-30),A:A,"<="&A3)
or only for the last 30 days:
=IF(A3<(MAX(A:A)-30),"",SUMIFS(B:B,A:A,"="&(A3-30),A:A,"<="&A3))


Regards
Claus B.
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