logman question, NIC bytes sent/received

I have written a VBScript to control startup of logman to gather various
performance counters. Specifying a counter such as:
"\Network Interface(NIC_NAME)\Bytes Sent/sec"
requires an instance name for NIC_NAME. I can retrieve various fields from
the WMI class Win32_NetworkAdapter but I haven't found a field that works
when used as NIC_NAME. Can anyone tell me how to retrieve the right
instance names for possible multiple NICs on one host?

HM