Do you mean when you're editing stuff, or as an effect to your movie while it's playing?
If no. 1, I think you hold CTRL-SHIFT and use your mouse wheel. If no. 2, you'll probably have to put everything on your stage inside a movieclip that you can then increase the scale and position on at your desired speed. I'd probably do a loop, increasing xscale and yscale until it reaches your desired size.