Are you looking for some form of encryption?
If you open a file in LabVIEW, you can set the file locking (optional input: "deny mode") to determine if other applications have simultaneous access to it or not while it is open in LabVIEW. If your OS supports it, you can also set the access right using "access rights.vi".
Maybe I don't understand the second part of the question but if the data is lost, no one can read it anyway or it wouldn't be lost. Right?
Could you explain in a bit more detail what you want to do.