How to make a resizable textfield?

Hello, I have situation like two textfield, one for input and the other for output. Then there comes the problem that for single line input, I type a long sentance but when it shows in the output textfield(because the length is limited there), it only can show part of the text.

So could any one who has some experience give some suggestion how to deal with this kind of thing?

Is it possible to define the length of the output textfield change according to the input textfield? Or is it possible that when the input textfield has more text than the output textfield required, then the text shown in the output textfield automatically change into smaller font size?

Does any one know how to make it? Thanks very much in advance!!!