SSO from Portal to ERP - Display Message instead of Logon Screen if user doesn't exist in backend

Hi All,

We have SSO configured from portal to backed ABAP systems.

Usually when UserID doesn't exist OR User Account validity expires in the backend system will show a logon screen to enter user credentials.

My question is, Is there a way we can show a custom message to user instead of logon screen? How can we achieve this?

Thanks,

Satish