Hello,
I need more information on your setup to give you better input.
Are you going to open the webconference page on the same computer that you use to brodcast your radio?
If not. What it comes to my mind is to use another PC on the same network, use some software to record the audio and then, stream it to your broadcast PC.
You consume the audio from winamp and that should be it.
If you need to do it all from one PC then we might need to find software that routes audio sources and stuff. You might need to buy some license for these kind of software.
So please let me know your current setup so I cand find better solution for you.
Best regards.
Félix