validateValue : function(value) return alert 3 times
===

I am using extjs version 3.1.0.

I create one simple code, which show alert message, if length of text entered is 12.
suppose i entered (123456123456), then it is showing alert message i.e(**Test**) 3 times.
My complete code is 


    Ext.onReady(function() {
        Ext.QuickTips.init();
         var searchForm = new Ext.form.FormPanel({
         id: "searchForm",
         renderTo: Ext.getBody(),
         items: [ {
              id: "itemUpc",
              fieldLabel: 'UPC',
              xtype: 'numberfield',
              labelStyle: 'font-size: x-large',
              height: '35px',
              name: 'itemUpc',
              validateValue : function(value){
                 if(value.length ==12){
    	       alert("Test");
    		return false;
    		}  
    	    return false;
    	   }
             }]
        });
    });

Please help me.

