GetSide returns for the constants Up, Down, Front, Back, Left, Right a xyzArray, which holds the points reponding to its side. In order you can iterate over the values 0 to 5 to get all sides of a box. The Sides are clockwise orientated relative to a "screwvector", who looks into the box.
xyzArray a; for ( int i = 0; i < 6; i++) { a = GetSide(i); .. do something with a for example: draw it }