this is not valid code.
the line:
$eCart = new eCart_Definition("eCart", 0, "$row_Settings['Currency']", "", true, 2, 0, "oz", true, 2, 1, 0);
should be:
$eCart = new eCart_Definition("eCart", 0, "".$row_Settings['Currency']."", "", true, 2, 0, "oz", true, 2, 1, 0);
but that will still give you an undefined index error unless you have the reocrdset on every page. You should use a set session value behavior to store the curency in a session, then use this code to set the cart object:
$eCart12 = new eCart12_Definition("eCart12", 0, "".((isset($_SESSION["currency"]))?$_SESSION["currency"]:"$") ."", "", true, 2, 0, "oz", true, 2, 1, 0);