>Considerable effort was put into troubleshooting this issue on affected machines, without success.
>
>The final resolution was to replace Excel automation with the use of Greg Green's VFPx class: https://github.com/ggreen86/XLXS-Workbook-Class .
>
>My gut feel is the future will see increasing restrictions/lockdowns on inter-process communications, function calls, automation etc both by Windows and by security/AV programs. My recommendation would be to eliminate Excel automation where feasible and replace it with this class.

Since xlsx (and other *.*x formats) are just a zip of a set of folders containing xml files, how hard would it be to just have a template and replace contents.xml only? Would that work?

I haven't studied the format too deeply (except once when I had to pull a long sheet with documentation out of a pdf converted into .odp presentation, which is a similar set of xml files), and I guess M$'s xml is anything but standard. And I actually don't have to mess with Excel, since export to csv works for most of what I need. My users want data for further analysis, not sales reports :).

And yes, I'm actively avoiding automation as much as possible. The only exception are automated mailmerges, which are a nightmare, because every new version of Word brings some new incompatibility - more dialogs which don't respect the setting and appear invisibly when oWord.visible=.f., interactive things (like recovered/recoverable documents list, again no programmatic way to get rid of that and it still appears in automation - but why, there's nobody at the helm) etc etc.