Protecting excel-vba application with a key for distribution

Question

I want to distribute excel workbook, protected with an activation key

This is the steps of my idea of protection.

1. I want to create a key generator to activate the use of the workbook using this data

   a pass provided for myself
   
   activation date
   
   username
   

2. When the workbook is open, ask for the first key my generator creates, so they need to contact me to get the key to use the product.

3. When the key is entered, the excel workbook must

   a) locks to the location the workbook was saved to work,

   b) changes internally the activation key using this criteria.

   activation key
   
   a pass emmbeded in code
   
   username
   

In this way when the workbook is copied to other location, even in the same computer, will ask for a new key, before work, because of the change of location and the change of password. I must prevent be "saved as" to protect it even more. I will developed to work to excel 2007 or higher.

How do you see my idea?

I never worked before doing that things, so, I need suggestions, example code, and all the stuff you want give me, to achieve the goal.

Answer 1

Excel protection is not designed to handle this kind of scenario in a secure way: its only meant to handle casual user errors.
The only secure way of handling this is to convert the Excel application to a compiled DLL: although using obfuscated .NET comes close.