System.Diagnostics.PerformanceCounter performanceCounter1; 
performanceCounter1 = new System.Diagnostics.PerformanceCounter(); 
performanceCounter1.CategoryName = "Network Interface"; 
performanceCounter1.CounterName = "Bytes Sent/sec"; 
performanceCounter1.InstanceName = "3Com 3C920 Integrated Fast Ethernet 
Controller [3C905C-TX Compatible] - Packet Scheduler Miniport"; 
performanceCounter1.MachineName = "sha-lion-01"; 

MessageBox.Show(performanceCounter1.NextValue().ToString());