Awesome! While I'm a little bummed that I no longer have a good excuse to implement this and brush up on my Django/JavaScript, this is exactly what I was looking for. Thanks.
Happy to see you reference Django - This is also what I got when an article suggested designing a Django site by implementing the URLs first, then the rest of the app to implement the URLs.
You may also want to check out Ledger (http://ledger-cli.org/). It's text based, but it would seem doable to use the powerful underlying engine in your project (it's open source).
If you'd rather have it be offline, drop me a line from the contact page and I'll send you an Excel version.