//回調函數，枚舉所有子視窗
function EnumWndProc(hWnd: HWND; lParam: LPARAM): Boolean; stdcall;
var
  WndClassName: array[0..254] of Char;
begin
  GetClassName(hWnd, @WndClassName, 254);//取得子窗口類名稱
  if WndClassName[0] <> chr(0) then
  begin
    if StrPas(WndClassName) = 'TTrackBar' then//判斷子窗口是否是TTrackBar
    begin
      SendMessage(hWnd, WM_USER 5, 1, 6);//發送消息，設置TrackBar的值為6
    end;
  end;
  Result := True;
end;    procedure TForm1.Button1Click(Sender: TObject);
var
  H: THandle;
begin
  H := FindWindow(nil, 'FormCaption');
  if H <> 0 then EnumChildWindows(H, @EnumWndProc, 0);
end;