How to post a system message to the SAP Portal version 7.0

Dear All,

Every month we have to shutdown our SAP Portal for maintenance and would like to know if it is possible to inform our users of this downtime via a system message. On the ABAP side I can do this via SM02 but is there a similar function in the portal itself without having to change the ABAP configuration.

Anyone knows how I can achieve this?

Regards,

Owen