Divorcing Input data from Programming

[Dr Wart Hoover]

I'm building an application in Excel 2003, for which I'd like to separate the input data from the programming (so that multiple users can use the same application with their own data - and I have a single protected & controlled version of the application).

It is highly likely that this will migrate to a later version of Excel one day, so I need to have one eye on the future...

The application does some pretty hefty number crunching & monte carlo simulations...

There are a number of ways to achieve this -

Present a button in the input file to load the Application
Get the users to run the application then specifty the input file
Other???
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Then, to get the data into the application

Use .csv file
Link to cells in the input file
Import data into arrays
Application to copy data into one of it's worksheets
Other???
​

Can anyone point me in the direction of what is considered best practice to achieve this? I'm looking at usability, supportability, not-crashing-the-pc-ability.