adding a field to Thanks page

I am trying to integrate PAP4 into my site, with their currency module, so i can record what currency products are sold in for my affiliates.

what i am trying to do is get amember to pass the currency to PAP4 on the thanks page, but I'm not sure what the variable is called.

This is the portion of the thanks page:

PHP:

<!-- display payment receipt -->
{if $payment.amount > "0.0"}


<script id="pap_x2s6df8d" src="http://localhost/pap/scripts/salejs.php" type="text/javascript">
</script>
<script type="text/javascript">
var sale = PostAffTracker.createSale();
sale.setTotalCost('{/literal}{$payment.amount}');
sale.setOrderID('{$payment.payment_id}');
sale.setProductID('{$payment.product_id}');

PostAffTracker.register();
</script>


#_TPL_THX_PAYPROC# <br />
#_TPL_THX_ORDERREF|{$payment.payment_id}|{$payment.receipt_id}#<br />
#_TPL_THX_DATETIME|{$payment.tm_completed|date_format:$config.time_format}#<br />

<br /><br />

{include file="receipt.inc.html"}
<br /><br />


{/if}{* END Of receipt display *}



I'm hoping to add somthing like:

PHP:

sale.setCurrency('{$vars.currency}');


after:

PHP:

sale.setProductID('{$payment.product_id}');


where the currrency value should be soemthing like "USD" or "GBP" or "EUR" etc.

Any ideas would be greatful

I use a variety, including paypal, monebookers.

all the products i sell have a 'currency' value that you set in the amember control panel, so i hoped i could extract this

Thanks! This looks like what i need

I set {$product.paypal_currency} in all products, so I should be able to get that info