# create the difference step into the past (add a \ before the ! in bash)
7z u {base archive.7z} {folder to archive} -mx=9 -u- -up1q1r3x1y1z0w1!{decrement.7z}

# update the Archive to the latest files
7z u {base archive.7z} {folder to archive} -mx=9 -up0q0x2