CATS Function Module

Hello Friends,

I have a requirement related to time entry in CATS on the portal. The system should allow the employees to go beyond 4 weeks in the past and enter time. Is there some kind of a user exit or a function module which can restrict the employee from entering time in the past? I did change the CATS profile by setting up the lower limit but it works only on the SAP backend but not on the timesheet portal.

Regards

naveen