stephen,
if you really want to address the additional rpm via the software section you would need to modify the sles 11 media a lot. Here is a short doc from the cool solutions on how to create a additional installation source just to give you an idea about it:
SLE10: Create a YaST Installation Source for Auto Installation | Novell User Communities
Therefor I would put that rpm simply on the media and use the post or init script section to install it. Much easier and faster to implement.
Regarding the online update I have no idea because I do not use it and have not finished the SLES 11 autoyast file for our company.
Rainer