Geocaching mode on the GPS allows you to mark a cache as 'found'. It changes the icon and creates an entry in the calendar.

Choose menu-menu-setup-geocache. Pick the icons you want for unfound geocaches and found geocaches. Configure your software to send geocaches with that icon. Now when you find-geocache, it will present a menu of ONLY the waypoints with an icon that matches your unfound geocache selection. When you have found the cache, just select "found" and the unit will change the icon, making it disappear from the nearest unfound list.

This family of GPS receivers is very popular among geocachers. This family is well supported by programs like GSAK, the Geocaching Swiss Army Knife and GPSBabel