Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

function AddThousandSeparator(S: string; Chr: Char): string;
 var
    I: Integer;
 begin
   Result := S;
   I := Length(S) - 2;
   while I > 1 do
    begin
     Insert(Chr, Result, I);
     I := I - 3;
   end;
 end;

 procedure TForm1.Button1Click(Sender: TObject);
 begin
   Edit1.Text := AddThousandSeparator('400500210', '''');
   // -- 400'500'210 
end;


 // Other possibility / andere Mцglichkeit: ThousandSeparator := ''''; 

 label1.Caption := FormatFloat('#,###,###.###', 23453452);

 // --> 23'453'452