Macro use for formulas and multiple files

Hi, I've never used the excel macro, I have 400 files that have the same column structure, but each one contains a different number of rows. I want to automate the same calculations/formulas across all spreadsheets for multiple columns inside the spreadsheet, for example adding new columns with formulas and automatically filling them down to the last row containing data in each file. What would be the best way to do this in batch? Would VBA/macros in Excel be the best option, or is there a better alternative? If possible, I’d appreciate an example of a script to apply formulas to every file inside a folder in batch.