Managing updated documents

[CthragYaska]

I've had a bit of a search in the forums, but couldn't find anything relevant; any advice on handling documents that get updated (specifically, remembering where you got to).

Example situation:

I have a source text file that I convert to MOBI and transfer to my Kinde 4NT via USB. I read it on the Kindle, and it tracks how far I've got (e.g. page 18 of 20).

At a later date, more content is added to the end of the text file (e.g. adding 15 pages to the original 20 pages). This is converted and transfered to the Kindle.

What I would like to happen is that the next time I open that document on the Kindle, it remembers that I *was* at page 18 (of 20) and continues from there (although now it is 18 of 35).

I'm guessing/seen mentioned elsewhere that the .MBP file holds the last-read position (and deleting this when updating the file triggers the "NEW" tag on the Kindle's home screen). However, simply updating the MOBI (leaving the .MBP in place) does not remember the position (is there a checksum of some kind in the MBP so the Kindle "knows" that it no longer applies to the accompanying MOBI?)

I'm presently using Calibre (0.8.30) command-line tools (plus my own text-to-HTML preprocessor) to convert the files, but just transferring them to the Kindle "manually" over USB).

Any help appreciated (I'm up to mangling the MBP file, if this would do the trick).

Thanks