I'm out on the edge of my knowledge, remember. Printer Job Language docs can be downloaded from [link|http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=bpl04568|here] (scroll down a bit).
My idea was that you identify all the elements of your print as belonging to the one 'job', but I haven't tried it so I don't know how possible PJL would make it.
Wade.