'-----
Set Ndis = GetObject("WinMgmts:root/wmi").InstancesOf("MSNdis_LinkSpeed")
For Each obj In Ndis
WScript.Echo obj.InstanceName & ": " & obj.NdisLinkSpeed / 10000, "Mb/s"
Next
'-----
I'm not expirienced in wmi so you might ask in a wmi-related group.