Audio Routing from other Devices

I wanna shoot LTC Timecode into Unreal.
I’m using the Audio Capture Timecode Provider and a Media Profile.
I can route the Signal from an extern Device via Line_in to Unreal via Windows internal Route system : Unreal Audio Input = line_in. That works.
But what if i wanna use it on the same PC running e.g. Reaper (or other LTC source) So there’s no Line_In Option? Is there’s a Possibility to route this into Unreal? (using the system audio or similar)