Imagine a field involving data that some people are accustomed to seeing
numerically, while others prefer to search/sort alphabetically.

I have another field, "preference" where I ask, "Would you like to sort
numerically or alphabetically?" and that is supported by a static list,
string. (List Items: Alpha,Numeric)

Once one of those is chosen I fire "preferenceChosen" as an event.

Is it possible, on another field to have an "onEvent" for preferenceChosen
that sets the display Expression dependent on the choice?

something like:

if (form.getValue("preference") == 'Alpha')
field.setDisplayExpression(Alpha Numeric)
field.setDisplayExpression(Numeric Alpha)

1. Is it possible to set Display Expression? What's the syntax?
2. Would it properly reload the Display?