Небольшая программка на Delphi- нужна помощь

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Button1: TButton;
    Edit3: TEdit;
    Button2: TButton;
    Label1: TLabel;
    Label2: TLabel;
    SaveDialog1: TSaveDialog;
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  num: string;
  f: TextFile;
  FileSelected: boolean = false;
implementation

{$R *.dfm}

procedure TForm1.Button2Click(Sender: TObject);
begin
  if SaveDialog1.Execute then
  begin
    Edit3.Text := SaveDialog1.FileName;
    FileSelected := true;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
i : integer ;
Start , Finish : Longint ;
begin
Start :=Edit1.Text;
Finish := Edit2.Text;
if  not (Start ==  Finish ) then
 AssignFile(f, Edit3.Text);
 Rewrite(f);

for i:= Start  to Finish do
WriteLn(f,i);

CloseFile(f);


else
 MessageBox(0, 'Ошибка! Значения не могут быть равны', 'Ошибка', MB_ICONERROR);
end;

end.