[NumLock]

Код:

unit Unit1;

interface

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

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

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  AlphaBlend:=True;
  TrackBar1.Max:=255;
  TrackBar1.Position:=TrackBar1.Max;
  TrackBar1.OnChange:=TrackBar1Change;
end;

procedure TForm1.TrackBar1Change(Sender: TObject);
begin
  AlphaBlendValue:=TrackBar1.Position;
end;

end.