CO Extension OAF Orders page

Hi Team, I am working on Orders OAF page where the Order textinput field should be auto populated with sequence and prefix which are set in profile options for the particular responsibility.  I want to extend seed controller OrderCO but I don’t find submit and save button events in that OrderCO.  How to check that controller for extension for extension where I can handle the submit and save button events and calling in processformrequest method, I can store the sequence along with prefix value in segment1 column of the table.  Thanks, Akshay