Payment methods depending on the chosen shipping methods

Hello everyone,
I would appreciate your help since I'm new to OC. What I'm trying to do is not allow the payment method "COD" to be available when the costumer selects "Pick up from store" as a shipping method.

For the guest checkout, I think it's easier, since both shipping and payment options are in the same page, so it can be done with javascript. But for the registered user who goes from /checkout/shipping -> /checkout/payment, I must pass the variable. I initially tried to check if the $_POST['shipping_method'] from the form reaches payment.tpl but it failed. Then I tried to pass the $this->session->data['shipping_method'] from the catalog/controller/checkout/shipping.php to a $_SESSION var but it failed. Help please! It's possible that there is an easier way to it but I dont know it.

Thanks.

This is called "ship 2 pay".

I've discussed this some time back: Ship 2 Pay(?).

Thanks alot!