If you follow what mendhak first posted it goes like ... the page is a child of the master (sort of) the userControl is a child of the master so set a public method on the master that calls a public method on the userControl. call the public method on the master from the page AFTER the shopping cart has been updated that way the data is current.

It might seem painful but it is logical if you follow the chain of events raised each postback for each page/control. I often use puplic properties like p_load that I can call at any point in the event cycle.