bind combobox text

I have an editable combobox. How can I bind the text the user开发者_StackOverflow中文版 enters? I can only do binding when the user selects whatever it is they typed in...how can I bind it as they type?

<script>

    [Bindable]
    public var boundText:String;

</script>

<TextBox text="@{boundText}" />

This will set up a two-way binding so changes to the textbox's text are reflected in boundText, and vice-versa.