I've looked through all of the Programming manuals and cannot find what the command line is to set the "Ext RF Atten" (under the Inpur/Output key hierarchy). Using the E4440A and LabVIEW 7i with which I have tried the library call function, but that terminates all of my LabVIEW completely. All I want to do is send the command via a VISA write command, but can't find it anywhere. Please help. Thanks!