Is it possible to add more than one button directly to the chart?  right now I'm using: 
chart4.addEventListener("rendered", function(eventObject, argumentsObject) { eventObject.sender.ref.drawOverlayButton({show:1, message:"Zoom"});} );
chart4.addEventListener("overlaybuttonclick", function(eventObject, argumentsObject){getCombo1("zoom");});
to implement changing graphs. 
  
It seems like I can only implement one button on a single graph with this method. 
  
Is there a better way to do it? 
  
Thanks in advance.