Targeting object on main timeline from script within MC timeline

I’m trying to add functionality to a 3D carousel. There’s a movie clip that has a script on the first frame of its timeline, and I would like to add some code to target a textfield back on the main timeline. I’ve tried using “parent” but I get the following error:

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

The line of code looks like this:

parent.mcVideoControls.desc_tb.text = vidText;

“mcVideoControls” is the instance name of the clip and “desc_tb” the name of the textfield within it. Given that I can’t move all this code from its timeline, how do I go about targeting the clip/textfield on the main timeline?