API for PerfmonPort Object Instances

Does anybody here know what API method or other approach can be used to get the list of object instances applicable for specific object type returned by PerfmonListCounter method?

The RTMT tool does this great by giving you a list of CallManagers when you're adding CallsActive counter from Cisco CallManagers object or list of phones when you're adding a counter from Cisco Phones, etc.

My first though was that it's PerfmonListInstance method but it doesn't look like a right method as it returns an instance type of the queried object type.

    PerfmonListInstance  returns a list of instances of a perfmon object in a particular host. Please refer PerfmonListInstance