Parallel Comunication to GPIB instrument

Hi

We have a GPIB instrument (Agilent 33210A Function Generator) and we want communicate from 2 parallels process in the same vi, (2 parallel loops). In labview 2012

We try to use the "GPIB status" function to check when instrument is in listen mode. (We check the LACS bit to determine when the instrument is in listener mode)

In my program we have  a principal loop and a secondary loop. The principal writes different frequency data to the instrument and the secondary loop try to write a frequency when the instruments is "free".  Sometimes it's works and sometimes it doesn't work.

How is posibble to make it? Do anybody in here knows a smart way to do it?

Thanks you very much!