Monthly Report Formatter

Problem Description

The finance team produces a monthly summary report as an Excel workbook and needs consistent, professional formatting applied automatically before it is distributed to stakeholders. The report has a fixed layout: row 1 is a title merged across all columns, rows 2–3 contain column headers, and rows 4 onward contain data.

A Python script needs to open an existing workbook, apply the following formatting, and save it:

1. Center the horizontal alignment of the header rows (rows 2–3)
2. Apply a continuous border around the outside of the entire data range (rows 4 to the last data row)
3. Set the header rows' background fill to a medium blue color using an RGB hex value (0x4472C4)
4. Set the header text to bold and white (0xFFFFFF)
5. Save the workbook in the modern Excel format (not the legacy .xls binary format)

The team uses the script on multiple machines running different Excel versions, and they have had bugs in the past when integer constants were hard-coded and produced unexpected behaviour after an Office update. Write the script so it is robust to version differences.

Output Specification

Produce a standalone Python script named format_report.py. Use a placeholder workbook path such as r"C:\reports\monthly.xlsx". The script should require only pywin32 and the Python standard library.