The deterministic part (calculations) is done by Excel.

The non-deterministic part is turning human instructions ("calculate the NPV over 10 years for X given Y") into Excel.

This is already a non-deterministic process (humans are non-deterministic!). The question is if an AI model can be more reliable than humans, and I can't see any reason why it wouldn't be.

The correct path is pretty clear, so the logits for following that path are going to be a long way from off-path.

For something like this the real problem is training the model to use Excel (which will show up by it being confused which sheet it is on or trying to use the wrong window or things like that), not the non-determinism.

"The non-deterministic part is turning human instructions ("calculate the NPV over 10 years for X given Y") into Excel."

erm theres an NPV function built in excel.