Currently, the "Analyze Volume" tool "Only" allows you to use an ORD Geometry Shape for a boundary. It would be much more useful and intuitive if we could also use a fence and/or a regular MicroStation shape for a boundary as well like you could with InRoads. There are several reasons for this, but one example is that many times the boundary that we desire is not just a simple shape, and we often need to generate the boundary from something in a referenced model (perhaps a bunch of different fill toes or something). In this case, we usually copy in the all the linework that we want to use as a boundary, and then using MicroStation, create a complex shape from that to use as a boundary.