i do the exact same thing with my album list...
try this string:
$if($stricmp($left(%_directoryname%,15),Various Artists),Various Artists,$if($stricmp($left(%_directoryname%,3),VA-),Various Artists,$if($stricmp($left(%_directoryname%,3),VA ),Various Artists,Single Artist)))|[$if($stricmp($left(%_directoryname%,15),Various Artists),%album%,$if($stricmp($left(%_directoryname%,3),VA-),%album%,$if($stricmp($left(%_directoryname%,3),VA ),%album%,%artist%)))]|[$if($stricmp($left(%_directoryname%,15),Various Artists),[$num(%tracknumber%,2). %title%],$if($stricmp($left(%_directoryname%,3),VA-),[$num(%tracknumber%,2). %title%],$if($stricmp($left(%_directoryname%,3),VA ),[$num(%tracknumber%,2). %title%],%album%)))]|$if($stricmp($left(%_directoryname%,15),Various Artists),,$if($stricmp($left(%_directoryname%,3),VA-),,$if($stricmp($left(%_directoryname%,3),VA ),,[$num(%tracknumber%,2). %title%])))
you might have to modify it, but basically it can tell if it is a various artists from the directory name (if it starts with "VA-", "VA -",or "Various Artists")
i havent taken the time to add any special tags to my music to tell it that way.
only additional thing i need to add is the name of the artist on the tracks of the various artists cds