In case you land on this question in 2023.

JohnWilson's macro code is good, but it has a major flaw (it's MS, not really JohnWilson).

It will mess up the formatting for any text that it replaces (bold, italics, underline, font size etc. will change to the text just before the pattern being replaced). Unless you have a Powerpoint with no formatting, this macro has limited use in the real world. The worse news is that there is no easy / good solution to that problem.