Hi Madhu,
I hope you are well and many thanks for using the SAP Discussion Forums 
.
Can you please refer to my colleague's SAP KBA: 2024498 - Clarifying UWL Refresh Options.
The SAP KBA above should provide you the options you can implement to automatically refresh the list.
Kindly update me as per your findings.
Kind Regards,
Jinnyre Malazarte - Enterprise Portal Support Engineer
Follow Jinnyre Malazarte