@SMcNeill Thank you for the working example. Very helpful. I appreciate your time and effort on it. The info you put in the Excel file example gave me a good laugh. You have humor!
This gets me well on my way to were I need to go. Interestingly, I found that the numerical values (like the number 50) end up under \xl\worksheets\sheet1.xml (in this case, because the one sheet in the file is named "sheet1") rather than in xl\sharedSrtings.xml. As an aside: I also found that the XLSX files saved by Excel and those saved by LibreOffice Calc differ somewhat in what extra stuff is included in sharedStrings.xml. It will take me some studying and testing to figure out how the format works and were the items go. Again, your working example has given me an excellent starting point and I am very grateful.
Thanks also to everyone else who has chimed in. I appreciate any additional pointers and input anyone may have.
LM