Select Audio Output as input device for FvoiceModule::CreateVoiceCapture

CreateVoiceCapture only works for me on one microphone, regardless if I change the default microphone on windows or change the “DeviceName” in C++ to a device. It only works for me when leaving it blank.
Is there a possibility to select my speakers as audio input, so sounds played my other software can be used as direct input?

Thanks a lot!