JQuery :: Custom Invalid Validation / Using JQuery Plug-in Validation?

Is there a method in jQuery that I can customize an invalid validation myself instead of using jQuery plug-in validation?

For example, if the form is valid do this below.

$('form').validate();
if ($('form').valid()) {
//do something
};

But if I wanted to have a cutomize invalid method I could do this below.

$('form').validate();
if (!x == y) {
$('form').valid() = False; //[:(]
alert('Form is not valid.');
};