Accesing a text field from a custom class

hello everyone.
i have encountered the following issue:
in a document i have 2 instances of different movie clips, one named inputArea and one named inputButton. both symbols from the library have been shared for ActionScript, and I assigned to the inputButton a custom class, which I built in a separate .as file.
the problem is that I cannot reference inputArea from my custom class, getting an error message:

1119: Access of possibly undefined property inputArea through a reference with static type flash.display:DisplayObject.

i tried to type root.inputArea but that didn’t work…
if anyone is able to help i would be grateful