Great. Many thanks all, I'll try and give each of these suggestions a whirl over the weekend.
Basically the reason behind my request is this: I keep books as EPUBs. I edit them, give them a 1 star rating when they're OK, then upload to my Kindle to read and do final proofing. They're converted to AZW3 for the upload. Afterwards I delete the AZW3 so that if they need further editing I will edit the EPUB and reconvert before uploading, to avoid accidentally uploading the old AZW3. However I then need to see which books have been changed "recently", but it turns out that they
all have since I deleted the AZW3... so I end up resorting to pencil & paper to keep track...
