1. <script language="JScript">
2.     function fnIShellDispatch4ToggleDesktopJ()
3.     {
4.         var objShell = new ActiveXObject("Shell.Application");
5.         
6.         objShell.ToggleDesktop();
7.     }
8. </script>

1. uses ComObj;
2. procedure TForm1.Button1Click(Sender: TObject);
3. var
4.   vShellApplication: OleVariant;
5. begin
6.   vShellApplication := CreateOleObject('Shell.Application');
7.   vShellApplication.ToggleDesktop;
8. end;

http://blog.sina.com.cn/s/blog_589d32f50100a7d9.html