Synchronising into tresor

Hi! I want to create a backup of an open folder(A), that contains many files. It might be documents, audio files or anything. I create the tresor, make a destination folder(A+) to mirror the folder(A). First time it is fine, I just copy all files there. Done.

Later I want to update the backup folder (A+) just with the updated and changed files from folder(A). Usually I use “synctwofolders” for that. It compares for new files and different creation dates or modification dates.

When I open the tresor (containing (A+) every file in the folder(A+) has the creation/modification date of the moment, when I open the tresor. So “sync2folders” can not identify changed files while comparing with folder(A) because ALL files in folder(A) are now older then the files in (A+). Impossible to synchronise this way. All I can do is to copy all files every time.

Is there a way to do what I want? Syncing an open folder with a folder inside a tresor?

Thank you for hints! Mac OSX…