If the map used on the details page is the GMap-Listing widget, then the range would be based on the Map Zoom Level setting. So all listings from all categories (or a selected number of categories) that fall within the selected map Zoom Level would appear within this map on my details page. If this is not possible, perhaps a 3rd map widget can be created that has this feature, GMap-Details? It would be the exact same as the GMap-Listing widget, only this would have the option to select categories to include/hide.