如何访问 controls.ControlAtomString变量 ( 积分: 100 )

如何访问 controls.ControlAtomString变量,

uses
Windows,
SysUtils,
Classes,
Controls;

{$R *.res}

function MyFindControl(Handle: HWnd): TWinControl;
begin
ControlAtomString:=WindowAtomString;
ControlAtom:=WindowAtom;
Result:=FindControl(Handle);
end;

编译器提示ControlAtomString未定义
[DCC Error] Project1.dpr(24): E2003 Undeclared identifier: 'ControlAtom'
[DCC Error] Project1.dpr(24): E2003 Undeclared identifier: 'WindowAtom'