Get "Use Billing Address" from shipping address section of Onepage checkout - magento

Question

I'm trying to get the gift option message to only show up when a customer is shipping to an address that's different from the billing address in the Onepage checkout flow. I can get the "Ship to same/different address" from the billing section with
$this->getQuote()->getShippingAddress()->getData('same_as_billing')
and it works great. However, if a customer makes it the shipping methods, and hits back to change the shipping address, that field doesn't seem to get updated. I tried checking
$this->getQuote()->getShippingAddress()->getData('use_billing_address')
But that data doesn't exist. In fact, when I have these two lines in additional.phtml:
Mage::log("Same as billing: ".$this->getQuote()->getShippingAddress()->getData('same_as_billing'));
Mage::log("Use billing: ".$this->getQuote()->getShippingAddress()->getData('use_billing_address'));
It doesn't trigger when I go from Shipping Address to Shipping methods. Can anyone give me some direction here?

Answer 1

I ended up using a javascript function instead of PHP, since it doesn't reload the page to get to each section.
In template/giftmessage/inline.phtml, I added the following:
function _showHideGift() {
var flag=document.getElementById('shipping:same_as_billing').checked;
if(!flag){
document.getElementById('gift-messages').style.display="block";
}else{
document.getElementById('gift-messages').style.display="none";
}}
And then called the function below the block inside of the CDATA, with the toogleVisilibityOnObjects calls.