the store order summary behavior stores the ID of the order that is inserted in a session variable. If that session does not exist, it performs an insert, if that session does exist, it performs an update.
you could add a store order summary behavior to the page and set the trigger to before page load, then on the bindings tab, set the value of the column to update to 1, This will really only work though if the only way to get to this page is after the order summary has been set initially.