Hello Avram,
Is the message one that you have crafted (i.e., and instruction item at the end of the questionnaire) or is it the automatic message the ML generates? If it's the former, then smacats suggestion should handle it.
If it's the automatic message, and you have each questionnaire in the experiment file, I wonder if you are having trouble with how the .exp file is running. Are you requesting to run the experiment, or are you requesting to run a single questionnaire by accident?