判断文件是否正在运用

function IsFileInUse(fName : string) : boolean;
var
   HFileRes : HFILE;
begin
   Result := false;
   if not FileExists(fName) then
      exit;
   HFileRes := CreateFile(pchar(fName), GENERIC_READ or GENERIC_WRITE,  
               0 {this is the trick!}, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
   Result := (HFileRes = INVALID_HANDLE_VALUE);
   if not Result then
   CloseHandle(HFileRes);
end;