pitchstring = finale.FCString()
pitchstring.LuaString = "A#5"
writtenpitch = true
for e in eachentrysaved(finenv.Region()) do
   if e:IsNote() then
      -- Quick trick to assure single notes at chords
      e:MakeRest()
      e:MakeNote()
      -- Set the pitch of the single note
      e:GetItemAt(0):SetString(pitchstring, nil, writtenpitch)
      e.CheckAccidentals = true   -- Assure proper accidental refresh
   end
end