Text effect

I am trying to create a simple text effect whereby a screen swipe makes the text gracefully slide into view when moving to a new frame.

I have attempted to do this by creating a movie clip called text-swipe-mc which is a grey square, the same colour as the background, and giving it a shape tween along the time line so that it collapses from a square into a line. I added an actionscript stop command to the last frame in the movie clip. I put this movie clip over the text on each frame.

It seems to work on some of the frames sometimes but is inconsistent:

http://www.holtconstructionltd.co.uk/dev/

Is there a better way for me to do this? Any advice greatly appreciated.