map load order

[cohiba]

First, let me say I am a complete GPS noob.  I recently got my first GPS unit (a Garmin Oregon 450).  I have custom maps, basemaps, city nav and 2008 Topo maps.  As I understand it the order the maps appear in the map setup list dictates how they are layered in the map view.  If so, is there a way to change the order of the maps?  If this is not the case, is there another way to "layer" maps.  For example, if I have both topo and city enabled, I olny see the city map but I thought it would be cool to have the topo map layered over the city map.  Thanks.