RichT wrote...
Looked into using INDIRECT, but with 365 .csv files (1 for each day)
that is
not going to work. Is there any way to do this without having to open
the
.csv file first??

Is it really so difficult to test?

It's not possible to use explicit/hardcoded external reference links
into closed CSV files, e.g., formulas like

='x:\y\[z.csv]z'!AB321

If explicit references won't work, derived references have no chance at
all.

Your *ONLY* choices a
1. open all 365 (366 in leap years) CSV files, like it or not;
2. write a macro to read through these CSV files in sequence, storing
desired values in worksheet cells;
3. use something other than Excel to do the data extraction into a
summary CSV
file, and open/import that in/into Excel.

Actually, there's another option: convert all these CSV files to XLS
files. There are techniques for extracting data from closed *XLS* files.