Automated Excel Financial Report Generator

I need a custom data-analysis tool that ingests raw financial data—monthly ledgers, balance sheets, transactional CSVs—and transforms it into clear, well-structured Excel reports. The core function is report generation, not advanced forecasting, so speed, reliability, and clean formatting matter more than complex predictive models.

Workflow
• The tool should accept common flat-file inputs (CSV or TSV) as well as direct database connections if that is simpler for you to implement.
• After ingesting the data, it must run a repeatable set of calculations: totals, averages, period-over-period deltas, and variance analyses.
• Output is a single Excel workbook containing multiple tabs (summary dashboard, detailed line items, and any charts you think add value). Formulas should remain live so users can drill down or tweak as needed.

Technology
Python with Pandas and openpyxl is fine, but VBA, R, or a compiled language works too—as long as the final deliverable runs on Windows 10 without extra licensing fees.

Acceptance criteria
1. Feed a sample dataset and receive a populated .xlsx file in under two minutes.
2. No hard-coded file paths; inputs and outputs must be selectable.
3. Workbook passes a quick spot-check against manually calculated totals (±0.01%).
4. Brief README covering setup, dependencies, and how to extend the calculations.

Please keep the code modular and well-commented so we can expand it later (for instance, adding PDF export). I’m ready to provide anonymized financial samples once the structure is confirmed.