1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:

...
  protected
    procedure WndProc(var Message: TMessage); override;
...
implementation

procedure TForm1.WndProc(var Message: TMessage);
 begin
  if Message.Msg = WM_MOUSEWHEEL then
    begin;
      if Message.WParam>0 then n:=n+1 else n:=n-1;
      Edit1.Text :=IntToStr(n);
    end
  else
    inherited WndProc(Message);
 end;					

1:

  if PtInRect(MyShape.ClientRect, MyShape.ScreenToClient(Mouse.CursorPos)) then					

1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:
34:
35:
36:
37:
38:
39:
40:
41:
42:
43:
44:
45:
46:
47:
48:
49:
50:
51:
52:
53:
54:
55:
56:
57:
58:
59:

unit Unit1;

interface

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

type
  TMyShape=Class(TPAnel)
     Private
      FShape:TShape;
     public
     procedure WMMOUSEWHEEL(var Msg: TWMMOUSEWHEEL); message WM_MOUSEWHEEL;
  End;
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

{ TMyShape }

procedure TMyShape.WMMOUSEWHEEL(var Msg: TWMMOUSEWHEEL);
begin
      inherited;
      if Msg.WheelDelta>0 then
        Color := clred else  Color := cllime;
      Caption := IntToStr(Msg.WheelDelta);

end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  With TMyShape.Create(self) do
    begin
      Parent := self;
      left := 0;
      top := 0;
      Width := 100;
      height := 100;
      ParentColor := false;
      ParentBackground := false;
      DoubleBuffered := true;
      SetFocus;
    end;
end;

end.