I am not sure how familiar you are with GDL programming, but this task requires quite good knowledge of it. You need to programme property script which results are accessible through Archicad calculate menu (properties,descriptors,etc...). I have not actually done anything like that in GDL so I can not show you an example. If you were after a solution something like 'var=volume()' ... 'print var' in 3D/Master scripts it will not work.
I know, I didn't help you much....I think you should more explore property script help or so.
::rk