Hello, thanks for your solutions.
I had an unknow problem with interoperability between C3D and Navisworks.
I tried making an elementary surface with just a closed pline in C3D to test if all surface's properties i need will be exported in NW(3D Area, 2DArea). Then NWCOUT to open the file in Navisworks and set a QTO to estimate quantities.
Well, no properties in NW as next image. Just solid's volume is shown.

I partially solved installing latest versions of C3D e NW.
This reasearch is for my civil engineering's thesis, i have to make a road model in C3D and estimate quantities in NW.
And if it were possible, to create an intelligent model able to give road costs in Navisworks quantification.
I did that customizing XML property files as is explayned here
http://help.autodesk.com/view/NAV/2018/ENU/?guid=GUID-B04BF605-1303-4A49-805E-5D6EF2801057
Later i customized quantities takeoffproperties.xml to made new item (cost), then customize takeoffpropertyMap1.xml to to allow the software read properties i need.
Finally i tried two ways to trasform quantities to costs in NW's QTO, the first is linking an Excel's file to the model, the other is giving extended data properties in Civil 3D.
Second way is better, this is an image

I thought interoperability was easier between Autodesk softwares. Anyway we are lucky to have the possibility to have a free version for students and to learn very interesting things.
Thank you all for your assistance.
M