Referring to premade textbox in object

1

I have an mc “mc” that I made in flash. It has a text box in it with instance name “txt1”. I dimmed a variable var mc:MovieClip = new mc() and used the add child method to add it to stage. Now I want to refer to the text box in the mc. I tried mc.getChildByName(txt1).text=“abc” but it gives me errors. How do I refer to that text box. Please tell if there is even a way to do so or not.