i've tried to control volume on an iPAQ pocket PC but i can't.

i can get the system current volume by using waveOutGetVolume() but can't set the custom volume by using waveOutSetVolume function.

the result message after waveOutSetVolume function is correct! ie the message is "MMSYSERR_NOERROR" but the system volume is not changed. --;;

how can i control the volume on an iPAQ? any ideas?