Excel Financial Report Validator Add-in

I need an Excel add-in that verifies if the totals of balances in a financial report match the subtotals. The validation should work for both vertical and horizontal totals.

Requirements:
- Secure .dll and .msi setup delivery
- Option to choose error handling mechanism (error message, highlight mismatches, or generate report)
- User preference for automatic or manual re-check after worksheet changes

Ideal Skills and Experience:
- Proficiency in developing Excel add-ins
- Experience with .dll and .msi packaging
- Familiarity with Excel formulas and validation techniques
- Strong programming skills, preferably in C# or VBA

Please share any relevant samples or videos.