ActionScript 3.0 :: Add Text To A Draggable Mask?

I want to add a line of text to a small mask - the mask reveals a portion of an image underneath - the user drags the mask around the stage

2 movie clips

1. an image that fills the 900x700 stage

2. a 200x200 rect with blur that acts as a "window" to the image

The code below works fine (almost - see comment) but how do I add text to the mask?
 
img_mc.mask = mask_mc;mask_mc.buttonMode = true;img_mc.cacheAsBitmap = true; // for the blur
mask_mc.addEventListener(MouseEvent.MOUSE_DOWN, dF);
mask_mc.addEventListener(MouseEvent.MOUSE_UP,

[Code].....