[jQuery] DWR + jQuery validation plugin

[Taras]

Hi,

Please advise, how it is possible to integrate DWR (Direct Web
Remoting http://getahead.org/dwr/) into JQuery validation?

I need to validate if such username is already existed in database
(ajax validation)
I was trying to do it in this way:

1)create dwr function

           function isUsernameExisted(username){
                var id = $j('#id').val();
                DWRUserManager.isUsernameExisted(username, id, {
                        callback:function(dataFromServer){
                        if(dataFromServer!="<c:out 
value="${SUCCESS_VALIDATION_MESSAGE}" /
>"){
                                return true;
                        }else{
                                return false;
                        }
                        }
                });
        }

2) add new validation rule to jQuery validator
                 jQuery.validator.addMethod("correctUsername",
function(value, element, params) {
                          return isUsernameExisted(value);
                }, "Please enter different username.");

3) register this validator to username field

$j("#userForm").validate({
          rules: {
            title: {
                correctUsername:        true,
                }
.....


But it doesnt work to me, because for jquery isUsernameExisted()
function always returns 'undefined' because it doesnt wait while
callback is executed.
So, is it possible to add new validation method to jquery validator
and make it capable for using my  isUsernameExisted() DWR function ?

Thanks,
Taras