I share your same yearning for a code equivalent of the book. However, I think writing the book using only Excel was a smart move on his part, simply because:

1) Excel is "visual" in the sense that you can watch the data change as you tweak things. There is no command line or program to execute, it's all happening live

2) For programmers, there's no "well I'm a python guy and this book is written in Java so it's not for me." None of us as coders really depend on Excel for writing code (basically) so it's kind of a way to take the technology decisions out of the equation. It's just the techniques.

All that being said, it's not trivial to port the logic of a spreadsheet over to code, and I think if anything that would make a great followup book.