JQuery :: Validation Not Bound To A Specific Form Field?

I'm using Validation plugin from [URL]

I'm trying to implement a validation in my form, but that should not be bound to an specific field. in fact, I have three input type=text, and I need at least one of them to be filled (like a conditional 'required').

I could create a new validation method, like:

$.validator.addMethod("foo", function(value) {
// short version:
return field1.value + field2.value + field3.value != "";
}, 'required');

[Code].....