APEX

Hi there,
I use a plsql procedure within a process so that the users can fill the category field for all selected customers (within an array) with a value from a list.
Sometimes this category value has already been set and it is not updated within the process, so I want to display a customized message afterwards, like '10 out of 15 companies updated'.

But as far I was only just using the Process Success/Error Messages. I've read about the apex_application.g_notification, but how and where to set it? Within the procedure?

Any help is appreciated,

thanks,

Lena