Protect Intellectual Property of an Excel Spreadsheet for Distribution

Background: An Excel spreadsheet for distribution has been protected with passwords on the worksheets & the VBA project. Also, the application requires the user to enter a Registration key on first use. While this is OK to stop the casual user from uncovering what should remain hidden, a more determined user can easily remove or replace passwords for both the worksheet and VBA project. Aim: I am wanting to make Excel more secure than it is. The method used for this would need to achieve a balance between: ease of implementation, cost of implementation, and ease of use for the customer. Other Considerations: Later, there may be a need to use MS Query to retrieve data from a password protected website. An Installer may or may not be needed. Is it possible to make the spreadsheet modular, so that the end user can add features later without having to start again? Some methods that I've come across, but not knowing much about them: 1) Using a “front-loader?? workbook, see “Professional Excel Development?? by Stephen Bullen. On page 873, ‘ the front loader opens the rest of the workbooks, supplying the password.’ ‘Use a front loader VB6 EXE to start Excel and open our password-protected application workbooks, keeping the passwords hidden within the compiled VB code. Passwords should not be stored as plain text, but in an encoded form…’ ‘Once started, we use VB6 DLL’s for most of our application features…’ 2) Distribute application in multiple files rather than in a single file, eg Storing VBA code in an XLA file and worksheets in an XLS file. Open both files when the application first starts and the code executes from the XLA file while the user interacts with the XLS file. 3) Using COM Add-Ins Described in MS Article 256624, “HOW TO: Use a COM Add-In Function as an Excel Worksheet Function?? And Article 238228, “How to build an Office 2000 COM add-in in Visual Basic ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform Excel 97 or later, on Win ME or later.