in general to show the panel according to some server side actions you should use showWhenRendered attribute pointed to some boolean property in the bean. When need - you setting it to true and reRender modal panel.
Thanks to both of you for your replies. I think I am thinking too hard on this, solution might be easy.
Ilya: By server side event do you mean running a Thread in backing bean with predetermined time and opening a modalPanel based on thread timing out? I am not aware of any event Servlet or JSF API provides for pre session expiration event.
Juan: I can't use jQuery, have to stuck with technologies I currently have, and jQuery is not one of those.
Any other ideas....
Thanks to All,
use a4j:jsFunction component
Great!!! that will make code more readable. I want to show a counter on modalPanel that will start from 2:00 minutes and down to 0. On zero I will close the modalPanel and execute the a4j:jsFunction. Any idea about that? I do not have luxury of using jQuery.