Using PDH API to collect performance data via WBEM/WMI

Hi,

I am writing an application to collect performance data from remote machines
through PDH APIs. I can tell PDH library to use WBEM/WMI as the real-time
data source by invoking PdhSetDefaultRealTimeDataSource(DATA_SOURCE_WBEM).

My problem is with collecting performance data from a remote machine that
has a administrative user credentials different from that on the local
machine.

After telling PDH to use DATA_SOURCE_WBEM, how do I request PDH library to
use a different user credentials to login into the remote machine? It looks
like CoSetProxyBlanket is one call that will do this - but how do I get hold
of an IUnknown pointer (to be passed to CoSetProxyBlanket) when using PDH
APIs?

Can someone please clarify this?

Thanks,
Karthigeyan