print options

hello

    i working on customizing print , i have icon on toolbar
i when ever i click it should directly , go to print (it should not open 
the dialog box)

i checked in browser.xul , toolkit.jar , browser.jar
there is cmd_print command ---> oncommand="PrintUtills.print();" (which 
opens the dialog box)

  i want know how do i change the command to print directly ,
   how do i do it

i want customize paper size to 8x6 , once it prints out the paper size 
8x6 it should stop


thanks in advance
hemanth