Flash cs3 Masking

Hi, I have been working on a logo that has a pipe image looping up and down in a zig zag. I want to create a mask that would allow me to make it look like water is filling through the pipe from the start of the pipe(bottom of image) to the top of the pipe. I've created two pipe images, one white which is the original look of the logo, and one blue. I made a mask on a motion line and I have it following the blue pipe, it works, however the mask is only a small square, and only shows a bit of the blue pipe at a time. I would like to reveal the entire blue pipe slowly to give the illusion of the white pipe being filled with water! PLEASE HELP!!

Either you build the mask dynamically, or you build it on stage.
Since second approach is much easy, this is what you have to do.
Duplicate the pipe form symbol and place it into the mask.
Make inside the mask like 10-15 key frames (or how many you think you need) and then starting from first key frame, chop from the pipe form.
In first key frame you chop a lot, so that only a small fragment will be the mask, in second frame chop a little less, and so on, until in last frame you have the pipe form. So it will be like a progressive pipe, growing from a small part to full pipe.
Then, when you want to simulate the water filling the pipe,
just use myMask.gotoAndStop(myMask.currentFrame + 1); // as3
or myMask.gotoAndStop(myMask._currentframe + 1); // as2
And of course, stop the mask in first frame.

Thanks alot, I'll give it a try!