another way is to group your VC parts in a group called "interior"... then, group your exterior parts in another group called "exterior"
basically the hierarchy will look just the same as if using felix's method, doesn't really make a difference... just 2 ways of doing the same thing

oh, and when grouping, don't forget to set the groups pivot points to 0,0,0... same as with the dummy
c ya
Moach