I don't know the answer to your question, but you may want to look at the following post to the J forum where Harvey Hamish posts a partial solution. To see the desired result I had to alter the code there by inserting a single space in front of each of Harvey's to labels, like this.
labels =. ' label 1'; ' label 2' NB. prefixed a space http://www.jsoftware.com/pipermail/programming/2008-December/013138.html -- (B=) ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
