Switch personnel number functionality in ESS/MSS

We are implementing hte Travel and expenses functionality in ESS. We ahve the switch personnel number link active in the home page framework. I would like to generate a message on the screen if somebody who does not have the right authorizations tries to click on the link. Right now, we get a java dump saying 'Critical error

A critical error has occured. Processing of the service had to be terminated. Unsaved data has been lost.

Please contact your system administrator.

You do not have the authorization to start service sap.com/ess_tratri/ChangePersNo. "

Is there a way to give out a nicer message that they do not have authorizations. Can a backend BADI be customized?

Thanks in advance.

PS: If this is not the right forum for this kind of messages please direct me to the correct forum.