To the point: Excel is a application interface that people are comfortable
with and that (thankfully) isn't going away any time soon. As a result when
dealing with certain custom applications, using the Excel interface is just
the way to go.

Question: Assume I wanted to write a custom application in Excel and deploy
it to 1000 people (since Excel 2007 is already on everyones desktop). In the
past we would have to write VBA modules and bake them into the spreadsheet.
That doesn't scale when attempting to deploy to 1000 users. People would copy
the spreadsheets everywhere and updates would be a nightmare. How do I get
around this issue? How can I leverage Excel to write scalable and
maintainable software?

Any help pointing me to resources explaining how to approach this would be
appreciated.