I think I have found a work around. As I have set the assignment of the subject variable "eCartCheckoutForm_ship_county" on the confirm page and "PayPal_ExpressCheckout_ship_countypp" on the pp_confirm page the following code seems to be working. My concern was potentially having the tax charged twice if eCart (the page) found both session variables matching. If you have another suggestion I would, of course, be glad to hear it otherwise I will try using the below.
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//eCart Rule
function WAEC_cali_cart_NyonondagaSalesTax() {
$totalTax = 0;
if (true && (((isset($_SESSION['PayPal_ExpressCheckout_ship_countypp'])?$_SESSION['PayPal_ExpressCheckout_ship_countypp']:"") == "NYONONDAGA")) && ((isset($_SESSION['eCartCheckoutForm_shipping_state_province'])?$_SESSION['eCartCheckoutForm_shipping_state_province']:"") == "NY") || (((isset($_SESSION['eCartCheckoutForm_ship_county'])?$_SESSION['eCartCheckoutForm_ship_county']:"") == "NYONONDAGA")) && ((isset($_SESSION['eCartCheckoutForm_shipping_state_province'])?$_SESSION['eCartCheckoutForm_shipping_state_province']:"") == "NY")) {
$totalTax += ($this->GetTaxableTotal() * 0.08);//Result
}
return WA_eCart_FormatNumber($totalTax, $this->ForceDecimalsC, $this->DecimalPlacesC);
}
//eCart Rule