Volume slider using Core Audio - cocoa

Question

I would like to implement volume and gain sliders in my Mac app. I already use code that sets the volume/gain to a specific level and tried to use it sample code with my sliders, but the volume/gain never adjusts, even though I can see the values from the sliders being passed to the routines. So what's the best to achieve continuous volume/gain levels using Code Audio?
Thanks
AudioObjectPropertyAddress address;
AudioDeviceID deviceID;
OSStatus err;
UInt32 size;
UInt32 channels[ 2 ];
Float32 volume;
SSAudioDevice * targetDevice = [self getTargetInputDevice];
address.mSelector = kAudioHardwarePropertyDefaultInputDevice;
address.mScope = kAudioObjectPropertyScopeGlobal;
address.mElement = kAudioObjectPropertyElementMaster;
deviceID = targetDevice.deviceID;
if(!targetDevice.ioLevel){
volume = 0.5;
}
else{
volume = [targetDevice.ioLevel floatValue] / 100.0;
}
size = sizeof(deviceID);
err = AudioObjectGetPropertyData( kAudioObjectSystemObject, &address, 0, nil, &size, &deviceID );
if ( ! err ) {
address.mSelector = kAudioDevicePropertyPreferredChannelsForStereo;
address.mScope = kAudioDevicePropertyScopeInput;
address.mElement = kAudioObjectPropertyElementWildcard;
size = sizeof(channels);
err = AudioObjectGetPropertyData( deviceID, &address, 0, nil, &size, &channels );
}
if ( ! err ) {
Boolean hasProperty;
address.mSelector = kAudioDevicePropertyVolumeScalar;
address.mScope = kAudioDevicePropertyScopeInput;
address.mElement = kAudioObjectPropertyElementMaster;
hasProperty = AudioObjectHasProperty( deviceID, &address );
if(!hasProperty){
}
address.mElement = channels[ 0 ];
hasProperty = AudioObjectHasProperty( deviceID, &address );
if(!hasProperty){
}
address.mElement = channels[ 1 ];
// returns true, channel 1 has a VolumeScalar property
hasProperty = AudioObjectHasProperty( deviceID, &address );
if(!hasProperty){
}
}
if ( ! err ) {
address.mSelector = kAudioDevicePropertyVolumeScalar;
address.mScope = kAudioDevicePropertyScopeInput;
size = sizeof(volume);
address.mElement = kAudioObjectPropertyElementMaster;
err = AudioObjectSetPropertyData( deviceID, &address, 0, nil, size, &volume );
if(err){
address.mElement = channels[ 0 ];
err = AudioObjectSetPropertyData( deviceID, &address, 0, nil, size, &volume );
address.mElement = channels[ 1 ];
err = AudioObjectSetPropertyData( deviceID, &address, 0, nil, size, &volume );
}
}