SAP Logon and logoff details

Hi,

I have a requirement like , While loging to SAP one popup shold come for accepting some number. After that i need to store in custom table with the logon userid and the number which entered on the popup and date/time.

The same way i need to store the Logoff date/time in the custom table.

Please let me know the solution for this.

Thanks,

Naveen