To use your USB port for GPIB communication, you would need a GPIB-USB controller like
this one. You can use it in any number of programming environments such as LabVIEW, LabWindows/CVI, Visual Basic, C++, etc. SignalExpress, as far as I know, is primarlily used with DAQ boards and not GPIB though you can convert a SignalExpress program to LabVIEW and use it there with all of the GPIB functions that come with LabVIEW. You might also want to go to the
Instrument Driver Network and see if there's a driver already written for your scope. That might also influence your choice of software.