Transitions and masking using actionscript?

i was also wondering if it’s possible to make transitions with masks using actionscript?

i have section headers that i want to transition when certain buttons are clicked, and depending on what button is clicked, a new section header is shown. i put all the section headers in a movie clip, with different frame names, so when the button is clicked, it jumps to the different frame name of the movie clip.

for the transition, i basically want a wipe left to reveal the section header… and a wipe right to hide it… and to do this, i figure i’d need to mask…

so i put a mask over the movie clip and realized that flash doesn’t mask movie clips very well, when using masking layers… so it doesn’t really work properly.

is there a way to do this using actionscript? and if so, how? i know flash know has a setmask property for movieclips…but can you modify the mask property’s size??

thanks!