Hello You'd better use a RenderSupport and @AfterRender to create a javascript method call that will link your checkbox with the copyDetails() method.
Something like this, i guess : In a separate JS file injected via @IncludeJavascript copyDetails : function(techFirstId) { .... } linkDetails: function(checkBoxId){ $(checkBoxId).observer('click', ...); } And your page @Inject private RenderSupport renderSupport; @InjectComponent private TextField techFirstName; @AfterRender private void linkDetails(){ renderSupport.addScript('linkDetails(%s);' techFirstName.getClientId()); } Regards.