[NumLock]

Код:

uses
  ShellAPI,

const
  ABM_SETSTATE = $0a;
var
  pData: TAppBarData;
begin
  ZeroMemory(@pData, SizeOf(TAppBarData));
  pData.cbSize:=SizeOf(TAppBarData);
  pData.hWnd:=FindWindow('Shell_TrayWnd', '');
  pData.lParam:=ABS_AUTOHIDE;
  SHAppBarMessage(ABM_SETSTATE, pData);
end;