In this simple Macromedia Flash tutorial I will show you how to make a transition tween from any shape to a specific text.

1.
First we will start in frame 1 in the timeline, and make a custom shape, this shape will be the start of our effect, then it will transform into a text.

I started by drawing two ovals, dragging one over the other then deleted the top on, (this way you cut out the inner part of the shape) so you get kind of a moon shape as shown below.

2.
Now go to the timeline and at about frame 25 right click and create an empty key frame.

In key frame 25 with the text tool type in the text you want your shape to turn into.

3.
Click to select frame 1, go down to the properties panel, make a shape tween as shown below.

4.
Now we can see that the tween has a broken line (dotted line) this is because we need to break the shape in frame 1 and the text in frame 25 to a raw shape, so go to the first frame, right click the shape and choose break apart, you may need to do it twice, (you can see when its raw the shape will have a lot of small white dots when its selected).

Now go to frame 25 and repeat step 4.

5.
Now you will see that the tween should work, the line between frame 1 and 25 is straight, so try to test you movie.

you should now have a custom shape tweening into text.