[PyMOL] showing peptide planes

[O. J. Ganesh]

Hey everyone,
 
I checked the pymol wiki for this one, but didn't find it.   Is there an easy 
way to create/show the OCNH peptide plane throughout a protein (or maybe in 
certain sections of a protein)?   I'd like to make planes that look like the 
ones from Ramachandran Plot Explorer:
http://bosco.infogami.com/rama
 
Thanks.