I have a very large file with 40 million rows. I split the file into 40 workbooks with 1 million rows each. They have the same dimension of 10 columns. In the first workbook i created the second spreadsheet with the reference tables in order to run some formulas in the first spreadsheet. The formulas are running for each row and are placed in columns 12,13 and 14.
Is there a way that I could perform the same calculations ( run the same formulas in the same columns ) without opening every single workbook, creating a second spreadsheet copying and pasting values and then copying and pasting formulas in to first spreadsheet in the same columns 12,13 and 14 ?
How can I approach this issue ? I want to save as much time as possible by automising the process which will be exactly the same for every workbook ... any suggestion will be much appreciated !!

Many thanks,