We have some fields that change state as the data loads into the UI. They start out as text boxes and then change to combo boxes. What we ended up doing was mapping the field both ways. In the test, first we check for the text box, and if that's found, do the actions, and next we check for the combo box and if that's found, do the actions.
It might be better to do a WaitProperty of some sort, but since we're doing the same action either way, for us, it doesn't matter which kind of box it is at the time, just that we can get to it.