Ok thanks for sharing Kanopus, but i find the cheating way.
you can make a new folder than name per your map: ie: Indonesia map. then put the gmapsupp.img into this folder.
in other hand you put gmapsup2.img in garmin folder. then use it as ordinary. it will work. next time when you need indonesian map you just cut and paste to garmin folder after moving the gmapsup2 to the other folder..
this is the cheating way that i found..hope it will help the others