make it visible! how to :)

I've thought of an alternative method you could use.

Capture the profile of the sloped wall to use as a complex profile. Edit the Profile to create the void within the wall and save it. Now split your existing wall on plan into three giving the middle section of wall the same length as you want the void to be. Apply the complex profile to the middle section of wall. Unfortunately you will have to draw the lines that form the edges of the void on plan, but other than that it works well on plan, section and elevation, and will also display correctly according to the floor plan cut plane.

Hope that helps.

i actually thought of a same thing in this particular case - complex profiels, with more simple one, i can achieve that without cp thanks man btw do you know any good sites with ac tutorials?

The main ones are the very comprehensive 'Interactive Training Guides' (ITG) provided by Graphisoft - http://www.graphisoft.com/products/archicad/training_guides/

There are also a few tutorials listed in the 'Tips & tricks' section of the forum - http://archicad-talk.graphisoft.com/viewforum.php?f=8

The tips & tricks articles are generally kept on http://www.archicadwiki.com/ but there seems to be no easy way of finding them unless you know exactly what to search for!

Good luck!