Implementing Delta logic at Infopackage

Need to implement Delta logic in BW while extracting data from source system using only one infopackage  having concept of checking against date ERDAT & AEDAT (If there is any new record created or change in existing record should be picked in delta ).

It can be achieved by creating  two info-packages based on delta logic for ERDAT and AEDAT to retrieve data from source system.

However, I need to implement this delta logic at one infopackage not on two.