Try to create a source location folder which you use for an update of your destination archive.
e.g.
7za.exe a "x:\destination_archive.7z" -up1q0r2x1y2z1w2 "c:\source_folder\*" -t7z -ms=off -mx1
I use this line of code every day to update a 7-zip archive. You need to adjust the '-u' parameter to your needs.