Secure Cost Calculation Tool Development

I need a secure, user-friendly tool for my water tank specialist company. This can be either a web-based or desktop app. The tool should allow staff to input tank parameters (e.g., length, width, height, material type) and receive a calculated cost.

Key Requirements:
- Input fields for tank parameters
- Calculated cost display
- Core pricing logic provided by us (in Excel or pseudocode)
- Securely hide pricing logic to protect sensitive formulas
- Easy-to-use interface
- Prevent reverse-engineering
- Backend should be easily updatable for future parameter or product additions

Optional Features:
- Basic login system
- Deployment assistance

Ideal Skills and Experience:
- Experience in web or desktop app development
- Strong understanding of security measures to prevent reverse-engineering
- Ability to create user-friendly interfaces
- Experience with backend systems that are easily updatable

Please provide:
- Preferred development method
- Timeline (ideally within 2-3 weeks)
- Quote
- Examples of similar tools you've built

Target OS: Windows
Security Level: Moderate