Source Code 2 and Destination Code 2 have been created to help track and report on donations. Both can be used to help redefine a main Code into smaller subsections.
For example you may have a Source Code set up to track donations for an Australia wide campaign. You can then set up Source Code 2s for each of the different states. This will enable you to track the donations for the Nationwide using the main Source Code and by each State using a separate Source Code 2.