[jQuery] jQuery Validation - group input field validation

[jQuery] jQuery Validation - group input field validation


Hi,
How can I do validation on a group of input fields, as long as one of
the 3 fields have a value then it's valid,
I've managed to group them, but it's showing up with 3 error messages
instead of one. How can I get it to display just the one error msg for
all 3 input fields?
Here's my validation js.
    var container = $('#errorContainer');
    var validator = $("#contactform").validate({
        rules: {
            firstname: "required",
            lastname: "required",
            email: {
                required: true,
                email: true
            }
        },
        errorContainer: container,
        errorLabelContainer: $("ol", container),
        wrapper: 'li',
        meta: "validate"
    });
    // test either 1 of 3 contact method is provided
    jQuery.validator.addMethod('required_group', function(val, el) {
        var $module = $(el).parents('#contactform');
        return $module.find('.required_group:filled').length;
    }, 'Please provide either an email address, home phone or mobile for
us to get in touch with you.');
--------------------------------------------------
HTML below:
<form action="" method="get" id="contactform">
            <div class="error"></div>
            <ol>
                <li>
                    <label for="firstname">First name: *</label>
                    <input id="firstname" name="firstname" class="text" />
                </li>
                <li>
                    <label for="lastname">Last name: *</label>
                    <input id="lastname" name="lastname" class="text" />
                </li>
                <li>
                    <label for="email">Email Address: **</label>
                    <input id="email" name="email" class="text required_group" />
                </li>
                <li>
                    <label for="mobile">Mobile Phone: **</label>
                    <input id="mobile" name="mobile" class="text required_group" />
                </li>
                <li>
                    <label for="phone">Home Phone: **</label>
                    <input id="phone" name="phone" class="text required_group" />
                </li>
</ol>
</form>