How to animate masks? STUCK!

Hi,

I have the following logo:

I want to make an effect as the image is being traced on the screen, because it is letters interwined. I went to Flash MX, imported the image, made a layer above it, and made it a mask.

The mask layer is a white oval, and when I mask it, it shows up as I wanted, which is the only part of the logo shown is through the oval.

When I tried to make a motion tween or shape tween to the oval, it wont move in the path that I want. I want it to start at the top right, and move down to finish one letter, and go on from there. I just cant get it to move in the path I want.

Any help would be greatly greatly appreciated. I dont know what stupid mistake I am making, but am totally stuck.

The file is located here:

http://www.drpoef.com/temp/stuck.fla

Thanks in advance.