I'm not sure I understand why you need different strings. The full VISA Resource Name would be GPIB0::5::INSTR and this is what should be listed in MAX and available when you click the VISA Resource Name. I believe the ::INSTR is optional but I don't know where you got just GPIB0::5 in the first place. Did you manually type this into a resource name control? Normally, you would only have one place in the program where you would provide this anyway. At the beginning of the program, do a VISA Open or use the initialize function in the driver and then pass the duplicate VISA Resource Name output to other parts of the program using a wire.