Here's a quick sketch of how to do this. Suppose you have the following two
<batch> definitions in a file called mybatch.iqx which has been
registered as your active webscript:
<batch>
/ file = "A.iqx"
/ subjects = (1 of 2)
/ groupassignment = groupnumber
</batch>
<batch>
/ file = "B.iqx"
/ subjects = (2 of 2)
/ groupassignment = groupnumber
</batch>
You set the experiment's launch page up to use a query parameter called
mygroup as group id / for condition assignment. You do so in the process
of registering your script via the Web Script Wizard.
#1: Have Qualtrics forward to the experiment's launch page at the end of the first survey section like so:
http://research.millisecond.com/username/mybatch.web?mysubject=someuniqueidentifier&mygroup=1
This will invoke A.iqx (e.g. your practice GNAT).
#2: Have Inquisit send participants back to Qualtrics and set up Qualtrics to pick up where it left off. At the end of this second survey portion, forward to the launch page like so:
http://research.millisecond.com/username/mybatch.web?mysubject=someuniqueidentifier&mygroup=2
This will invoke B.iqx (e.g your test GNAT).
#3: Have Inquisit send participants back to Qualtrics as before. Note that a script can explicitly manipulate finishpage URLs via the defaults.finishpage property (see the language reference for details).
For information re. Qualtrics' handling of query parameters (generation and extraction, use for flow control), please consult Qualtrics' support materials.