Thanks. I ended up realizing I needed to figure out exactly what "minimally functional" spreadsheet would need to do.
Most of the Gui toolkits could handle displaying and entering data in a grid.
And after a lot of work I could likely expand one of the parsers to handle text functions. I'm sure to TJF adding text functions is trivial, but it isn't to me.
Then I realized that a basic minimum for me is to have autofilters, and I probably could fit something into one of the GUI girds.
I once wrote code to insert subtotals into a list, so I know I could handle that, but as I recall that code (written in scheme for the SIAG spreadsheet) couldn't handle anything unexpectedly complicated. I'm sure polishing it would be trivial to some, but not for me.
I probably could figure out how to have absolute and relative cell references in formulas. And this is what killed it for me. I could no longer just store the original formula, but instead a tokenized version so if a row or column got inserted, I could change the relative cell references to the new letter+number representation. I'm sure some wouldn't find that hard, but it is for me.
In the end, for the personal projects I had in mind, embedding was a nice to have, but not nice enough to warrant all that work.
For my part-time employer, I couldn't justify the cost of my programming time. Plus they love pivot-tables, but I hate them, so there is no way anything I wrote would suit their needs.
So I appreciate any tips or links so that I can reevaluate the do-ability given my programming skills, but at this time it is a big fat "Not Doable."
Particularly thanks for the link above, the linked parser does handle text and it does handle absolute and relative cells references, as well as references to cells in other tables. But trying to understand the C++ is more work that this project is worth to me.