Defining custom validation methods

Dear Support,
We just purchased metabox development version. It is very useful. In one of our website we need to use the metabox extension MB Frontend Submission & created a form. Now we need to validate the fields and your default validation rules came to help mostly, but we need to create a custom validation rule/method and had some experience creating them with addMethod function when I was using jquery validation plugin you mentioned, but it gives me error when I am trying to define a new rule with addMethod. Can you please help me in this?

Note: the error message is Uncaught TypeError: Cannot read property 'addMethod' of undefined at HTMLDocument.<anonymous> when I am writing the code as follows

$.validator.addMethod('checkXiiAggregate',function(element, value){
        if (check_all_XII_fields_empty()) 
            if ( element  == "") return true; 
        if ($("#cmbclassxiiyearofpassing").val() != $("#lte_current_year").val()) {
            if (element == ""){
                return false;
            }
        }
        return true;
    }, "Please provide aggregate marks.")

Thanks in advance