General Changing music from pen drive problem

[joaoguilherme]

Hello! When i put a pen drive to listen to my musics i can only change them using the buttons from the steering wheel and I can't change the musics using the radio buttons. The radio buttons only work when i am listeling to a radio and not the pen drive. How can change the musics from my pen drive using the radio buttons? Sorry for my English. Thank you.