m200 series MP3 players power by usb?

i am using the m240 player at my computer desk so i wonder if there is a way to listen to music or to the radio power by the usb instead of using the battery. it seems like once the usb is connected all functions are disable.

This works for me:  plug in the USB to computer, then gently slightly unplug until the computer disconnects the Sansa but the power remains.  I also can use my USB hub which, for no reason I understand, does not connect my Sansa to the computer, but provides power.