Protect or Lock .XLSC file when exit program

I am busy developing a program with potential commercial value where lots of data will eventually be saved/stored in the .XLSC file. Something that worries me is that the Saved.XLSC file is unprotected/not locked and can be opened with inter alia Notepad. What I found, while testing my program, was that If you delete, add or change one single character in the encrypted file, the whole file becomes corrupt and can never be used again. This is of major concern (especially if you already had a lot of date saved) because you would have to start from scratch! I raised my concerns about this issue via [email protected] (Request # 2339). The reply I received does not really address my problem (copied and pasted here):

“Yes, sure XLSC files can be corrupted this way, but it’s the same for normal Excel workbook files or any other file. By default, XLSC files are not configured to be opened with Notepad unless you associate them yourself. Why would your customers alter their save files, especially if they see binary characters?”

My concern is that there will always be that one in a million persons who will be curios enough, illiterate enough, stupid enough or whatever you want to call him, that through his ignorance, would fiddle around with the “garbage” (encryption) he found in the .XLSC file.

Can the developers of XLSPadlock maybe find a way to protect or lock the .XLSC file when you close, exit or quit your program.

A solution would be hiding save files with a hidden attribute. SetAttr statement (VBA) | Microsoft Docs
Thus, the file would not be displayed to users.