Invoice Macro Automation in Excel

I rely on a single-sheet invoice that already functions correctly, but every billing cycle I still key the same fields manually and then compile the numbers into a basic summary report. I’d like a straightforward VBA solution for Excel 2013 that:

• streamlines data entry into the existing invoice (e.g., button-triggered form or macro that places customer, item, quantity, price, and date in the right cells)
• generates a simple summary report from completed invoices—totals by month and customer in a new sheet—at the click of a button

Please build the macros directly inside my current file, keep the code well-commented, and include a short note explaining how to run each routine. The workbook must remain compatible with Excel 2013; no external add-ins required.