[jQuery] Validation

[jQuery] Validation


I have seriously been fighting this issue for hours. I would
appreciate some advice when someone gets a chance.
I am wanting to check my database to determine if this user already
exists. I thought I could just add the method to the validation.
Evidently I'm doing something wrong. Here is the code.
        <script type="text/javascript">
            $(document).ready(function(){
        var checkName = (function(value){
                var dataString = '?mode=checkUser&username=' + username.val();
                $.ajax({
                type: "GET",
                url: "user_formsubmit.php" + dataString,
                success: function(html){
                    if(html == "True")
                    {
                        return true;
                    }
                    else
                    {
                        return false;
                    }
                }
                });
                });
            $.validator.addMethod("checkName", function(value, element){
                return checkName(value);
            }, "This user name already exists.");
         $("#user_form").validate({
                rules: {
                    userName: {
                        required: true,
                        minlength: 8,
                        checkName: false
                    },