I’m still running an old Excel-based calculation and booking program that only behaves properly on Windows XP. Its many macros and hidden tables act like a miniature database, but maintaining it is now impossible and it refuses to run on my Windows 11 machines. I need the whole solution rebuilt as a clean standalone Windows 11 application while preserving three core pillars that make the file valuable to us today: all calculation logic, the booking workflow, and the underlying database management that ties client, price and schedule data together. The interface can evolve—slicker, more intuitive screens would be welcome—but the numbers must match the results produced by the legacy file. Key deliverables • Executable Windows 11 program that fully replicates existing calculations, booking process and data storage • One-click import of our current workbook so historic records carry over intact • Basic user guide outlining day-to-day use and any admin tasks (backup, adding new price tables, etc.) I can supply the original workbook, screenshots of its forms, plus a short video walkthrough so you can trace every step. I will test the finished build by running identical scenarios in both systems; outputs must be identical to sign off. If you’ve modernised legacy Excel/VBA tools before—especially by porting logic into C#, .NET, Python or similar—I’d love to see examples. Let’s bring this vital tool into the present.