Custom calculation not executing in Firefox

I have a custom calculation script in my pdf (Adobe XI):

     var v = this.getField("DefendantListBox").value;

     if( typeof v=="string" )

         event.value = v;

     else

         event.value = v.join("\n");

The script runs without issue on my desktop (windows).  When I embed the pdf in my web application via Firefox (33.1.1), the script does not execute.

I'm at a loss as to how to enable the Adobe Javascript within Firefox.