WMI Classes

Hi

I am trying to get a few performance metrics in Exchange 2003 and 2007. I am facing an issue though. Some of the WMI classes present in Exchange 2003 are not available in Exchange 2007.

Like for eg

Win32_PerfRawData_MSExchangeMTA_MSExchangeMTAConnections
Win32_PerfRawData_MSExchangeMTA_MSExchangeMTA
Win32_PerfRawData_SMTPSVC_SMTPServer

Any clue how to build the above WMI Classes in Exchange 2007 Server ??

Plz advice