function copy_billing_address_to_shipping(checkbox_name){
    var field_names = new Array('name','street','city','state','zip');

    if(checkbox_ref= document.getElementById(checkbox_name)){
        if(! checkbox_ref.checked){
           return false;
       }
    }

    for(i = 0; i < field_names.length; i++){
        if(bill_ref = document.getElementById('b' + field_names[i])){
            if(ship_ref = document.getElementById(field_names[i])){
                bill_ref.value = ship_ref.value;
            }
        }
    }
}