Here's the quick way:
On the "Thank you for your order page" Add...
1: A Repeater with Custom Query
2: Query of:
Select ##TOPN## ##COLUMNS## from
(
Select * from COM_OrderItem
LEFT JOIN COM_Order on COM_Order.OrderID = COM_OrderItem.OrderItemOrderID
LEFT JOIN COM_SKU on COM_SKU.SKUID = COM_OrderItem.OrderItemSKUID
) Temp WHERE ##WHERE## ORDER BY ##ORDERBY##
3: Where condition (hit the black arrow to go to macro editing mode) of:
OrderID = '{% Convert.ToInt(ECommerceContext.CurrentCustomer.Orders.OrderBy("OrderDate Desc").Where("DATEDIFF(minute, OrderDate, GETDATE()) < 15").FirstItem.OrderID, -1) |(identity)GlobalAdministrator%}
6: Make sure the Google Analytics API is loaded and any supporting javascript is there.
This will need to be done in design mode.
Note that the ideal solution would be to use Event Hooks, but this will limit to only that customer's latest order, and i believe in the ecommerce api it will ignore or simply update orders if you send it with the same identification.