.net - WP7 Custom Class UI Binding?

I have a map with a MapItemsControl in my WP7 app that contains pushpins bound to items in a collection of custom classes. The pushpins are bound to properties of the item in the collection via a DataTemplate.When an item is added to or removed from the collection, all pins display correctly, with properties as per bindings, but when just an items' properties are modified, the UI does not update. The bindings just seem to get values from the source item upon loading, but I'd like them to keep the UI elements updated when the source collection items' properties are updated.To illustrate, I'll create a similar example:

Heres a custom class:

Public Class Box
Property CurrentColor As Color
Property Location As GeoCoordinate
End Class

[code]....

Whenever I add or remove items from TempBoxes, the pins all render as they should (e.g. if I specify a color in the collection item, the pin shows the color).Tapping on the item triggers the BoxTouched sub, which causes the item's color to change in the collection, but the UI doesn't change (pin color stays the same).To get the UI to update the color, I have to get it to render the pins again, by adding something like this to BoxTouched:

BoxControl.ItemsSource = Nothing
BoxControl.ItemsSource = TempBoxes