Am I thinking of this correctly?^C^CPL 'SOWhen I make that into a custom command with PLS as the command name, it says "PLS" is not a valid command.What am I missing? 

What does PLS stand for?Why isn't it written as ^C^C_PLS

PLS would be my keyboard command for the station offset poly line commandpl - to get a polyline started'so - to have it function as a station offset polylinePLS would be what I'd call the command.

Does Civil 3D have the Macro Recorder feature?

You don't say how you made it into a custom command.  What you have would be appropriate to a menu item button in various places, but if you want to be able to type PLS at the Command: prompt, you need to define it using (defun ...), and within that, you can't use the macro-language form you posted.  It would need to be something like [I don't have the station-offset option, so you'll need to check the correctness of the option entry]:
(defun C:PLS ()
  (command "_.pline" "'so")
)
 
That should leave you in the command, at whatever prompt comes after selecting that option.

Is this similar to my other question on by layer commands?  (http://www.cadforum.cz/forum_en/forum_posts.asp?TID=10160&PN=1&title=custom-command-macro-help)So I need to create a .lsp to run these and then inject the loading of that command into acad2013.lsp?
ebrody2014-05-15 18:43:45