What program do you use for your air to ground or ground to air communications? I still have no clue how this much software interacts the way it does.
There seems to be several choices, is that the app you want on the headset?
EDIT
Please tell me what version of windows you are using i will then try to help you setup windows to play all sounds on your speakers then you can set your voice app(Squawkbox has the option) to use the usb headset for talking and listening to ATC. If you use another software list it and i will try my best to help you.
If you enter the options in SquawkBox you should see this option under voice. If you select your usb headset, it should send sound there, but windows needs to have its default settings to your speakers or else flightsim will still play on the headset too.
Using the dropdown list you should be able to select your sound card or the usb headset. The headset is what you want here. Set this only after windows has been set to use the speakers as its default audio device. Control Panel->Sound, Speech and Audio Devices->Sound and Audio Devices->Audio(tab)->Under Default Device, set your sound card.
Let me know how this goes.
EDIT EDIT.
VRC has an option too, just what you need
anyway, more help when i know what you use.