Are you looking for something like OUTPUT? http://msdn.microsoft.com/en-us/library/ms177564.aspx

I know in cases when you run an UPDATE you can use this to view the deleted.fieldname (old version), inserted.fieldname (new version) etc.

This may be way off base but could you add a column to your query and use CASE to populate it based on your A, B & C values? Then...