Hi Soumyajit,
Its a common issue in most of the projects.... Below are just my thoughts
Options left are .....
Educating the user not to use the PB during the job window.
Creating dedicated PA's for each timzones (If feasible)
Finding the right time to run the CVC when no one is using the PB.
Implementing LC lock and KF level locks.
Selections assigned to users should be with minimum planning objects and not wide open.
Restrict the no of users who are using the PB.
Going for Custom reports.
Check the below discussions
Additionally you can look at the report /SAPAPO/TS_LC_DISPLAY_LOCKS to display the locks and find out the users who are using the selections and ask them to get rid of PB (Though its a manual work before the job starts.)
Regards
Vinoth