SUMIF Formula Across Multiple Sheets

Originally Posted by El Guapo

I would like to do this without having to modify the formula every time I add a new property worksheet to the workbook.

The above is key. IMO you would be best served using some Events to keep the list up to date.

Similar thread/post from a while back: http://www.excelforum.com/excel-gene...le-sheets.html see attachment on post #17

Note: Volatile SUMPRODUCTs are generally bad news performance wise.
Sometimes better to replicate the SUMIF(s) on each individual sheet within a common range and subsequently conduct basic 3D sum of those SUMIF ranges (using "book end" sheet references)

Not sure what you don't understand.

Performing SUMIF in 3D requires an array of all sheets to be aggregated, e.g:

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becomes::

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However, given you explicitly state that you wish to:

a) add / remove sheets at will
and, in turn
b) do not want to have to manually update the formula each time

in my opinion it makes a great deal of sense to use a VBA Event to keep an up to date list of all relevant sheets.

The sample file in post #17 of the referenced thread does the above c/o of the following workbook driven event:

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The subsequent 3D SUMIFs utilise the Defined Range: _3DList as basis for sheet listing - in your case the formula would appear as:

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Unfortunately performing 3D SUMIF is inefficient and volatile ... an overview of your options: http://www.mcgimpsey.com/excel/threedsumif.html