Scheduling in Project

Hi,

I want that system should automatically populate Basis end date in the WBS element based on the end date of last activity assigned to this WBS,

Scheduling Scenario i am using is 2 - Top Down Scenario, so system is taking project start date as date on whihc i create the project, but end date remains blank? how can we setup the system so that this end date is also automatically populated.

Thanks in advance.

Warm Regards,

Jatinder