I think you need to take a step back and start with the basics. First, check your cable. Is it the right type? If you've got a DB9 to DB9, pin 2 on one end should be connected to pin 3 at the other and pin 3 would connect to pin 2. Second, check your com settings on the instrument. I don't know what the defaults should be but they should be in the manual. Third, before you try writing any code yourself, establish communication with the instrument using Hyperterminal or if they supply one, the Agilent program. I've seen no indication that you're even able to send a command to the instrument. Until that happens, you're not going to be able to read anything. Start with something simple like *RST. Set the instrument manually and if the instrument resets, you know that you're talking. The NI driver which you are reluctant to use, first sends the command SYST:REM to enable remote control. The default setting in the driver is for DTR/DSR handshaking so that's another thing you should try.
