Joel - you can of course in Excel have multi-char columns in Excel.
Columns got from A - Z of course, but when you past Z, they start over with A[A-Z].
If you’d exceed that, then it’s B[A-Z]… and so on.
For Example (here is a sum of row A out to 52 columns): ‘=SUM(A1:AZ1)’ the results is 52
This is a left to right thing, not a left to right and top to bottom of each column.
It is normally unusual to see, but some I have seen many from accountants with massive workbooks/spreadsheets.
So, you are correct in saying the range the OP is using is not correct, but it is because the OP is not asking for the column range but the row range.
So, this is really not a PoSH issue, but how the OP needs to call the Excel DOM which the OP needs to work through.
So, the OP must collect all rows and columns.
Example: “=SUM(A1:AZ3)”, which in my sample XLS is 156
Of course that 3*52 (row & columns) in that single row.
See this post.
Read and Get Values from Excel File using PowerShell Script
Or looking at the Excel docs and leverage the Range function from Excel.
More simply the OP could just do this: “=SUM(A:AZ)”
Not adding the Row number, means use the whole column.
One can easily see this by doing the selection natively in Excel and copy and past the formula.