sortOn when an array contains objects?

I have an array made up of generic objects; all of the objects have the same properties, one of which is a textfield (named, creatively enough, “textfield”).

What I need to be able to do is sort the array based on the text property of the textfield property, something like this:

listArray.sortOn("textfield.text", Arrray.CASEINSENSITIVE)

which doesn’t work. Can anyone suggest a functional way to do this? Thanks!