Growing dynamic text

I am trying to do an animation with text growing from small to large in the middle of the screen.

I can currently achieve this by converting text to symbols and using motion tweening to create the effect. However, I want to randomly allocate the text from a list of messages stored in an array. Using symbols wont let me dynamically change the text, and using dynamic text does not allow me to "grow" the text.

I have tried using the 'size' attribute of dynamic text to try for a similar effect, however since this changes the font point size, the effect is rather ugly.

Does anyone know of another way around this problem? Is it possible to convert text to symbols while an animation is running?

Kind Regards,
Michael