Excel Tool: Merge Customer Reports -- 2

I have three separate customer data reports that I download regularly. I need an offline solution—Excel-based is preferred, but I’m open to any lightweight desktop approach—that can pull the data from those three files, combine and clean it automatically, and then present the final results back in Excel across multiple worksheets.

Core needs
• A simple way for me to point the tool to the three source reports (file picker, drop zone, or even just pasting paths).
• Behind-the-scenes logic that matches customer records, removes duplicates, and reconciles any field name differences.
• Output to an .xlsx file with clearly labelled multiple sheets (e.g., Combined_Data, Exceptions, and any other logical splits you suggest).
• Everything must run fully offline—no cloud connections or add-ins that require an internet login.

Preferred tech
Native Excel features such as VBA, Power Query, or a well-commented macro will work fine. If you think Python or another local scripting language offers a cleaner approach, feel free to propose it as long as the end result is still an easy-to-open Excel file.

Deliverables
1. The working tool/workbook.
2. Brief step-by-step instructions so I can refresh the output whenever I have new reports.
3. A short change log or annotation explaining the main transformation steps, so future tweaks are straightforward.

Acceptance
I’ll test by feeding three fresh reports; if the combined output populates correctly across the designated worksheets with no manual intervention, the job is complete.