noncontiguous cells

[Vivian]

I need to sum up a column of noncontiguous cells.
(eg. G3+G6+G9+G12); with the result being presented at
the bottom of the column.

However, whenever I insert rows in between the data and
the row that contains the total sum, I need to manually adjust the summation
formula.(eg. formula above + G15+G18+G21).
On the other hand, when I delete the rows in between the data and row that
contains the total sum, a reference error pops up. (so I need to manually
adjust my formula again)

I have at least 50 columns to perform this summation for. Is there any sort
of formula that helps to minimize the manual labour?

Thanks you in advance!

[Mallycat]

However, whenever I insert rows in between the data and
the row that contains the total sum, I need to manually adjust the summation
formula.(eg. formula above + G15+G18+G21).

This doesn't seem right. Excel by default caters for rows being added. Can you explain the exact sequence of events, or post a sample spreadsheet

[Ragdyer]

Say that your datalist goes from G3 to G99.

You could enter this in G2 or G100, or wherever:

=SUMPRODUCT((MOD(ROW(INDIRECT("G3:G99")),3)=0)*INDIRECT("G3:G99"))

--
HTH,

RD

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"Vivian" <Vivian@discussions.microsoft.com> wrote in message
news:14890C5A-27A2-473B-A22A-30C6D27F2D15@microsoft.com...
>I need to sum up a column of noncontiguous cells.
> (eg. G3+G6+G9+G12); with the result being presented at
> the bottom of the column.
>
> However, whenever I insert rows in between the data and
> the row that contains the total sum, I need to manually adjust the
> summation
> formula.(eg. formula above + G15+G18+G21).
> On the other hand, when I delete the rows in between the data and row that
> contains the total sum, a reference error pops up. (so I need to manually
> adjust my formula again)
>
> I have at least 50 columns to perform this summation for. Is there any
> sort
> of formula that helps to minimize the manual labour?
>
> Thanks you in advance!