How to Set Microphone Gain

Hi
I am using DirectSound API’s on Windows2000 operating system. To create an
application to capture user Voice and its being used in real time framework.

To capture Voice i am using DirectSoundCapture object. But
it does not provide me the necessary framework for setting the Microphone
Gains. And in DirectSound API’s (version 7.0) there is no reference for
this.
Can any One help me for this , Its an open issue for me and i don;t know how
to work on it. Or is there some other ways to do the stuff.
I have heard that there is some thing known as KsProxy Filters and have gone
through the Windows 2000 DDK for it but it does not provides me enough
documentation for the implementing and using the filters.

Thanks a Lot before hand for the precious time u would invest for me .
regards
Shishir Katdare

P.S. :: If some one can just point me to the resources which might be
helpfull also would be a great help.