How to get Dispatch() to work?

Hello,

I have following, which doesn't want to work. The receiver never receives
the message. Why (code below)???

Thanks & regards,
John

// ---- The message ----
const
  WM_NUMUPDATE = WM_USER + 9989;

// ---- The receiver ----
type
  TMyEdit = class(TEdit)
  private
    procedure WMNumUpdate(var Msg: TMessage); message WM_NUMUPDATE;
  end;

procedure TMyEdit.WMNumUpdate(var Msg: TMessage);
var
  Control: TWinControl;
begin
  Control := TWinControl(Msg.LParam);   // Breakpointed here --> never
accessed!
  if Assigned(Control) and (Control is TMyUpDown) then
  begin
    Text := IntToStr(TMyUpDown(Control).Position);
    Msg.Result := 0;
  end;
end;

// ---- The sender ----
type
  TMyUpDown = class(TUpDown)
  protected
    procedure Click(Button: TUDBtnType); override;
  end;

procedure TMyUpDown.Click(Button: TUDBtnType);
var
  Msg: TMessage;
begin
  inherited;
  Msg.Msg := WM_NUMUPDATE;
  Msg.WParam := 0;
  Msg.LParam := Longint(Self);
  Dispatch(Msg);   // Check here --> Msg is OK
end;