convert excel worksheet calculator to a web application

I am a CPA and specialize in auditing workers compensation insurance costs for employers. I have replicated the NJ Experience Rating formula in excel for last 20 years and want to convert it to a web application.: The excel file contains 5 tabs. 1. Payroll input; 20 lines and 13 columns. 4 input columns; vlookup and other basic calculations. 2. Claim input; 34 lines and 14 columns. 5 input columns, vlookup and other basic calculations 3. Table of Rates; 600 lines; 8 columns for vlookup; updated each year. 4. Table of Factors; a few lines and columns for vlookup. updated each year. 5. Summary; 21 formulas; [add, subtract, divide, multiply, round] How difficult to save each client's data to revise claim amounts? Could cut and paste. Can formulas be protected so can't change or download? Was considering alternative approaches' client portals; auto reply email with download link. Will one of the "converter websites" be used? . caspio, spreadsheetconverter, etc. Hoping to charge a small annual user fee; Looking for marketing assistance [social media, emails]