=SUM(($A4=$A$2:$A$400)*($A$2:$A$400$A4-7)*($C$2:$C$400))
Your formula above is an array formula, which needs to be array-entered.
Click inside the formula bar, then press CTRL+SHIFT+ENTER (CSE) to confirm
the formula. If you do it correctly, you'd see Excel wrap curly braces: { }
around your formula in the formula bar.

In this instance, alternatively you could use:
=SUMPRODUCT(($A4=$A$2:$A$400)*($A$2:$A$400$A4-7)*($C$2:$C$400))
which can be normally entered, is just press ENTER to confirm the formula
--
Max
Singapore
http://savefile.com/projects/236895
xdemechanik
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"lothar" wrote:
I am wanting to sum a set of numbers for the previous 7 days. I am using the
following formula:

=SUM(($A4=$A$2:$A$400)*($A$2:$A$400$A4-7)*($C$2:$C$400))

When I look at the Function Arguments window it shows "Formula result =
214.5" (the correct value) but it displays "67.2" (the daily value) in the
spreadsheet.

Does anyone know what is going on and how to remedy it?