unit Unit1;

interface

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

type
  TForm1 = class(TForm)
  private
    { Private declarations }
  public

    Procedure Wheel(var msg:TMessage);message WM_MOUSEWHEEL;
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

Procedure TForm1.Wheel(var msg:TMessage);
var
  zDelta:ShortInt;
begin
  zDelta := HIWORD(msg.WParam);
  msg.Result:=0;
  Caption:=IntToStr(zDelta);
end;

end.