🚀 go-pugleaf

You can't do this with find/change: you'll have to use just find, then process the collection of found objects.
It's probably easiest to do it in two passes. Collect all description paragraphs containing ' and ' using search much in the way you do now:

      myFindAction = myStory.search(' and ', true, true, '', {appliedParagraphStyle:myFind});




Then change each found paragraph's preceding paragraph by adding an 's':



for( var i = 0; i < myFindAction.length; i++ ) 
   { 
   var prevPar = myStory.paragraphs.previousItem( myFindAction[i].paragraphs[0] ) 
   prevPar.insertionPoints[-2].contents = 's' 
   }



Repeat for comma. There are several other possibilities, this is just one.

Peter