Page 'Activated' event too late. Is there an earlier event for page activation? (Don't want user to see page updating)

Using UX Reactive Expressions I set the opacity and values on a page inside the page’s Activated event. But, when the user navigates to the page you see the changes take place which is not desired. I’d rather the page be updated before the page transition.

[The only way I’ve figured out how to do this–WHICH IS NON-IDEAL–is setting the values on the previous page before calling navigator.push().]

Activated has a very useful When property which should help in this case.