Thank you for patiently waiting. I just fixed the problem on this particular sample file. It appears that the sheet names have special characters or hidden characters that caused the 3D sum or 3 dimensional sum formula to fail.
In order to fix your issue, the sheet range needs to be enclosed with single quotes, like:
I created sample sheets and the format sum(sheet1:sheet2!A1) works fine. So I believe the problem is with the named sheets that you have. I believe these sheets are created by other programs and not created manually so that explains why the naming has issues.
Here is the attached fixed file:
Another thing that can surely help you in your 3D sum formula is by using wildcards. In your sample file, you can enter the formula:
And when you press Enter, Excel will build the correct formula for you. This works ONLY if the names of the sheets are in continuous numbering like your, N75736 and N75737.
I hope that helped.
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