Hello,
The easiest way to do this is to use NI-Device:
http://sine.ni.com/nips/cds/view/p/lang/de/nid/13047
This will allow your GPIB interface to behave like an instrument (which you define). You can pass controller in charge status from your controller to another interface or instrument which has controller capability, and then set up a polling or event waiting in order to simulate an instrument. For example you could read and ignore timeout errors, and then respond based on what you read. However, if you want to build the functionality of an instrument, NI-Device will give you more flexibility.
For an example VI which uses LabVIEW as a non-controller (GPIB Instrument):
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3D87556A4E034080020E74861&p_node=DZ52353
For information on passing controller in charge status, see:
http://digital.ni.com/public.nsf/websearch/873BE8238AD6B0BA86256B1B004DC203?OpenDocument
Thank you,
JLS