Hello again,
the way, the 7z.dll wants to be used is a bit strange, so I decided to give up trying to create some nice UDF for it.
But I found a much nicer way for using 7-Zip and it's great features for generating and updating archives. I re-used the source of 7zg.exe and created a new 7zg-mini.exe, you can find the documentation and the code here: http://mcmilk.de/projects/USB-Backup/ - search for 7zg-mini
It is a bit more code then normal, so I will not Post it here
And the USB-Backup there is an "AutoIt application" ... full source of it is also there... but most comments are in german, sorry.
with best regards,
Tino