If the "standard GPIB functions" means NI-488.2M (NI GPIB API) compatible or VISA compatible functions, the GPIB board vendor must supply an appropriate NI-488.2M-compatible API (GPIB-32.DLL) or VISA Library (VISA32.DLL) that supports the specific GPIB hardware. Actually some GPIB board vendors supply NI-488.2M compatible API but I don't know if QUANCOM do.
Assuming QUANCOM does not supply the compatible APIs, the only way is to use the vendor-genuine QLIB library. I believe the QLIB is provided as a DLL format therefore LabVIEW is basically able to access the DLL functions through Call Library feature. If QUANCOM supplies LabVIEW wrapper VIs for use with QLIB, you can simply use them. Otherwise, you will have to write the wrapper VIs by yourself.