How to run a VBA Sub

I have a VBA Sub I’d like to run on an existing spreadsheet

Read LibreOffice Help - Working with VBA Macros

It is better (an more efficient) to rewrite your VBA macros based on the StarBasic and the LO API functions.

API = Application Programming Interface

You can try to run the VBA macros with the compatibility options, but not all of the VBA macros will run.