Vista - return average badwidth value

Is there a way to return the current network usage of a server / PC nic?

e.g. 50% used?

I'm trying to write a script that will poll each server every hour so I can
monitor which servers are busiest during different parts of the day.

I dont think this script returns what I need. it has speed, but doesnt
return a value,

strComputer = "mycomputer"
Set objWMIService = GetObject("winmgmts:\\" & strComputer &
"\root\CIMV2")
Set colItems = objWMIService.ExecQuery("SELECT * FROM
Win32_NetworkAdapter", "WQL", _
wbemFlagReturnImmediately +
wbemFlagForwardOnly)


many thanks
in advance