In batch: Is it possible to use dll instead of txt?

First note: in modern versions of Windows, there is no such things as DOS. Batch files are hosted by a regular Windows protected-mode process. Using uneditable DLL files? Of course, but it makes batch programming totally redundant. You can create your own script host, or, better yet, just migrate to programming instead of scripting. For further talks, you need to tell us your preferred platform, language and other relevant detail. Don't forget to tell us what is your goal.
--SA