>Now, the question is:
>Is there a method to combine the two print jobs so as the printer may interpret them as an unique job and so perform the print-duplex operation (Drawing1+Back1(Sheet#1)+Drawing2+Back2(Sheet #2)…DrawingN+BackN(Sheet #N))?

Could you put the CAD stuff (whatever it is) into a vfp general field, and then run only the one vfp print job? Using a general field works with some things, but I have no idea about your situation. Won't cost too much work to try it, anyway...