Ajax like event for onLoad

[Brown, Berlin [GCG-PFS]]

I am using the Ajax Tabbed Panel class and I could possibly hijack the
"onUpdate/onClick" routines to suit my needs. 
 
But I was curious, is there an event/behavior  that I can call when a
panel loads or render.
 
Something along the lines of:
 
SomeAjaxPanel {
  onBeforeRender() {
    this.add(AjaxBehavior("onload') {
      onEvent(target) {
         ....
      }
   }
  }
 
}