How to play live voice samples on soundcard :: BargeIn

I am Mr. Kagzi and would like to know "how can we play live voice samples on sound card". I am recording the voice over telephone line and getting the voice samples. I would like to play those sample live on the speaker. How can we do it. If any body can have idea then do let me know. If you have any sample code then please send me. either in VB6, VB.Net,C,C++, or VC++. The main reason to do is to provide BargeIn facility in my recording application.

BargeIn is the techincal term used specially in Telecom/call centre industry, where it means when two person are talking, third person can listen the conversation of them through his phone or from computer using software.

Thanks