Excel /x

Normally Excel opens all spreadsheets in a single instance, but I had the need to open an Excel spreadsheet in a separate process.  Fortunately Microsoft added a startup switch, "/x", back in the memory-constrained 32-bit days, to allow multiple, very large spreadsheets to be open concurrently.  While that's not the reason I needed it (it's more than a tad geeky), I was glad to have it available and led me to the discovery of a number of other startup switches, detailed at the link below.

https://support.office.com/en-gb/article/command-line-switches-for-microsoft-office-products-079164cd-4ef5-4178-b235-441737deb3a6#ID0EAABAAA=Excel