Clearing a list lookup field based on a radio button

Hi all,

I have a form (Nintex Forms 2010) that has a radio button (options 1 and 2) and two list lookup fields (A and B). I would like to clear A and B when the option at radio button is changed.

I used the code below, but do not work

NWF$(document).ready(function()

{

var choice = NWF$("#" +Tipo);

choice.change(function()

{

NWF$("#" + ClassA).val('');

NWF$("#" + ClassB).val(''); ; }

);

} );

Any idea?