im using a jquery validation plugin
first i add the validation to the form:

$('#EmployeeForm').validate({
        rules: {
            "Employee.FirstName": "required",
            "Employee.PatronymicName": "required",
            "Employee.LastName": "required",
            "Employee.BirthDay": { required: true, date: true }
        },

        messages: {
            "Employee.FirstName": { required: "*" },
            "Employee.PatronymicName": { required: "*" },
            "Employee.LastName": { required: "*" },
            "Employee.BirthDay": { required: "*", date: "00.00.00 format" }
        }
    });

and then latter a need to add validation rules to other form elements:

$('#Address_A.Phone1, #Address_A.Phone2, #Address_B.Phone1, #Address_B.Phone2').rules("add", {
                digits: true,
                messages: {
                    digits: "?????? ?????"
                }
            });

but i get an error: 'form' is null or not an object

i check, the form and all the elements in it are created before i add validation to it.
cant figer out whats wrong.