How to send GPIB Interface Commands in Matlab

How do you send GPIB interface commands in matlab using the instrument control toolbox?

I'm using an old CV meter (Keithley 590CV) that responds to some particular low level interface commands, some of which directly control the TTL levels of individual GPIB bus lines (e.g. IFC is #9, REN is #17). Examples in the manual are given for instructions used when programming a HP-85 compatible machine with BASIC.

Command    HP-85 Statement       Description
 REN        REMOTE 7              Remote ENable
 IFC        ABORTIO 7             InterFace Clear
 LLO        LOCAL LOCKOUT 715     Local LOckout
 GTL        LOCAL 7               Go To Local
 DCL        CLEAR 7               Device CLear
 SDC        CLEAR 715             Selected Device Clear 
 GET        TRIGGER 715           Group Execute Trigger

7 is the interface code for GPIB in the HP-85 environment. 15 is the (factory default) primary GPIB address of the instrument. Hence the commands REN IFC GTL and DCL are broadcast signals received by all instruments on the GPIB bus whereas the remaining commands are addressed to a specific instrument.

The only command I found in the toolbox is trigger(), which sends a GET signal to the specified instrument. How can I send any of the other commands?

[Nick Martin]

Clemens - did you find a solution to this problem. I'm trying to interface with an HP 5334A Universal Counter that also requires low level interface commands and have had no luck. Any lessons learned that you're willing to share would be appreciated.