Frenchy Pilou
>>but you don't answer me about an automatic selection
Forgot about this. Sorry :)
When you asked me I tried to do this, but I couldn't done it successfully :(
When MoI joins separated parts it changes ID's of the faces. So I can't find which faces are new created.
At the moment I know only way to do it: create a new style. assign it to a new faces. join surfaces. restore selection. revert styles.
It will work, but I don't like this method.
I think we should ask Michael about this :)