Excel Rostering Program Enhancements

I have an automated Excel-based rostering workbook that has been running in production for a while, but a few critical pieces now need attention.

The core of the job is to refine the calculation logic. Some totals are coming out wrong, a couple of edge-case rules were never coded, and overall processing speed has slipped as the file has grown. I would like the existing formulas/VBA adjusted so every shift, allowance and overtime rule reconciles accurately, a set of new business rules is added, and execution time is brought back to an instant feel.

Alongside that, I need the import/export module expanded. At present it handles only a basic CSV; I want to introduce two additional formats (one XLSX template we use with payroll and a JSON summary we send to Power BI). Clean, reliable parsing and generation of these files is essential, with graceful error handling rather than silent failures.

Deliverables
• Updated workbook (formulas, VBA or Power Query as appropriate) with corrected and extended calculations
• Refactored code or macros delivering noticeable performance gains on a roster of ~2 000 rows
• New import/export routines supporting CSV, our payroll XLSX template and JSON
• A brief change log and test sheet showing the before/after results for key scenarios

Please keep all development inside the existing file structure unless a separate helper module is clearly justified, and comment your code so future tweaks are straightforward. If you have advanced Excel/VBA optimisation tricks or experience integrating Excel with JSON, you will be a perfect fit.