message bar in subcontroller / message-raising in other subcontroller

In my BSP-App, I have a message bar in which I display all messages that are raised in my application.

The messages are stored in a singleton-class with a messages table.

The message bar is in subcontroller A and loops over the messages table to display all messages in that table.

The rest of the application is in subcontroller B.

The prolem: subcontroller A is processed before subcontroller B, so if I raise a message in B, it is only displayed in A after the next server event, which is of course not what I want.

What can I do? Thanks for any help!