change_state = function(id, field){
 new Ajax.Updater(id+field,'/users/change_state', 
	 {asynchronous:true, evalScripts:true, 
	 onComplete:function(request, json){
	  $(indicator).hide();
	 },
	 onLoading:function(request, json){
	  $(indicator).show();}
	 ,parameters:'id='+id+'&field='+field});
}