This is a very abstract question and there are many different ways you could achieve this. They all involve manipulating the DOM of the viewlet itself though.

How you go about this depends on what exactly you want to achieve. You can use css to show/hide any of the existing links that you want to still be visible while the message is displayed. In addition, you will want to get a reference to a DOM node that can be used to display the message and populate it appropriately. Once you have the node ready, you will probably want to add a css class to it to control exactly where/how it is shown.

For more detail on this you should research DOM manipulation using javascript as well as the tools available through dojo and, more specifically, dijit._Widget (which your viewlet extends automatically by extending our Viewlet class).

Adam Archer
Jazz Web UI Developer