When i do what you say, the result volume surface is in the wrong elevation.
Example: my surface "1" is in (+-) elevation 235.600 and my surface "2" starts from 235.850 to 235.450 (it's like a cup), when i do the volume surface, the result goes to elevation 0.0 (+-), and when i do contour elevation 0.0, it gives me the interserction but in the wrong elevation! how do i put this in the right elevation? because what i want is the (surface 1)-(surface 2)
thanks for your time