[jQuery] jQuery.validate: If the A field is changed, how to call the validate method of B field?

[jQuery] jQuery.validate: If the A field is changed, how to call the validate method of B field?


There is a question: If the A field is changed, how to call the
validate method of B field?
In my form, there are A and B fields, I have to call B's remote
method, when one of A and B have changed,
coding:
    $(myForm).validate({
        rules: {
            B: {
                remote: function(){
                    return "/validateABExist.do?A="+$("#A").val()
            }
        messages: {
            B: {
                remote: "the combination of A and B is existed"
            }
        }
    })
    $("#A").change(function() {
        //TODO: How to call B's remote method?
    });