If you use the Data Shortcuts and reference one surface into the other
drawing it should work. You NEED to have the surfaces in the same file.
Matt Kolberg
"Grant C" wrote in message
news:4827525@discussion.autodesk.com...
> Can you do a volume off 2 tin surfaces that are in the same project but
not
> the same drawing or do you have to put both tin in the same drawing