Caution: As far as I am aware, there is no CAL3D exporter for AutoCad.
However, being an Autodesk product (and in the same family as 3D Studio Max), you should be able to export in formats that Max can read. And by extension, I believe Blender (free) can import certain Autodesk formats..?
What I'm getting at is that you won't find CAL3D tools for AutoCad, but that it shouldn't preclude you from working in that program until you're ready to export. When you get to that point though, be aware that you might need to look up exporter plugins or conversion programs in order to make it to a finished CAL3D file system.
