[NumLock]

в мему будет писаться только 1 раз:

Код:

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    TrackBar1: TTrackBar;
    Memo1: TMemo;
    procedure FormCreate(Sender: TObject);
    procedure TrackBar1Change(Sender: TObject);
  private
    { Private declarations }
    FPosition: Integer;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  FPosition:=-1;
end;

procedure TForm1.TrackBar1Change(Sender: TObject);
begin
  if TrackBar1.Position<>FPosition then
  begin
    FPosition:=TrackBar1.Position;
    Memo1.Lines.Add(IntToStr(FPosition));
  end;
end;

end.