Bulk search & replace question

[Capricorn]

Yesterday and today I have been trying to figure out how to do a bulk search and replace of certain text inside a larger number of epubs (about 100 for one text, about 310 for another text,..etc).

These strings of text are in the html files of the epubs.

I can do a conversion from epub to epub, and using the search & replace function, but discovered it also changed my stylesheets which I definitely do not want to happen.

The quality check plugin allows to do a search of the epub files, but does NOT provide a replace function.

So far I have used sigil to make changes manually, but it is taking ages.

I have searched in the forum here, but I do not seem to find the right information. Maybe I have used the wrong keywords to search for info.

Meanwhile my mind is becoming more and more confused from reading threads and trying out things, that it is time to ask the forum for help.

Can this be done in Calibre without using the conversion function? If not, are there other tools that would allow me to automate this search and replace? Any info would be much appreciated.
Thank you.

Capricorn