Find and replace to loop through subfolders too

Is it possible?

Yes.
For my opinion the code must be decomposed to several. 1. main code , 2 Subfolders enumeratre that must be recursive and 3 file processing
For subfolders you can use

Set FSO = CreateObject("Scripting.FileSystemObject")
Set Folder = FSO.GetFolder("C:\Program Files")
For Each SubFolder In Folder.SubFolders
    debug.print SubFolder.Name
Next