Hi @Vivian
I think the answer for your question can be found in this discussion, also there are some workflow files for you to utilize:
My example presents 2 methods:
one is a 1-line calculation and fast, and the other uses loop logic to make the calculations
Simply put,
You need the column number which can be found with .IndexOf() — dt1.Columns.IndexOf("column")
Then using number / 26 and number mod 26 you can determine the number to convert for both letters of the column.
Regards.