Hi,
Let's say your information is in sheet2 and you want the Q in sheet 1 so
enter the formula as follow

=SUM(OFFSET(INDEX(Sheet2!$1:$1,1,(COLUMN()*3)-2),,,,3))

hope this helps


"Jeff" wrote:

Can anyone devise a formula to summarize monthly data by adding each three
months? That is, I need to add columns A-C, D-F, G-I, etc. I've been doing
this manually, but there must be a better way. Thanks.