Textbox onDataChange not Detecting character changes

I'm working on developing a form with a textbox that has a custom drop down to display records. As the user types in the textbox, the drop down will be auto searching the records in the drop down with the string the user is typing. The on data change for textbox's only detected a data change on focus loss or if the user presses enter. I know that the typeahead component has this functionality of displaying a value list, and as the user types it will sort/search the list for every character change that occurs. Normally I would use a typeahead but because I need a custom drop down I cannot use it. So I am wondering if there is a way to detect character changes on a textbox?