How to command (row of ) instances of a mc (purpose to build a mask for transitions)

I am building up a mask mc to be employed in transitions , composed by many rows of movie clips.
I created a basic movie clip with a shaped triangle graphic whose widht / height was set to zero on 1st frame , to be enlarged at its max 6 frames after by means motion tween. (Time line of this mc is stopped at both ends)
Then I created another mc , that will be called maskmc , as only 1 mc can be employed for mask purpose.
This mask mc is placed on a mask layer onto the content to be shown and hidden during transitions.
Inside the maskmc there are several rows of the masktrianglemc movie clips instances arranged tightly so that there will be no gap holes in the mask.
Now it comes the challenge : to command every single movie clip in the row , to open and close the mask , it would be necessary to give different instance names to every instance of the masktrianglemc movie clip.
It would be a hard work to name one by one and it would be a poor job to place several lines of command in the frame of main time line to open and close the mask when necessary :

_level10.maskmc.masktrianglemc1.gotoAndPlay(2);
_level10.maskmc.masktrianglemc2.gotoAndPlay(2);
.
.
.
_level10.maskmc.masktrianglemc”N”.gotoAndPlay(2);

I wonder if there is a more inteligent and clearer way to accomplish this task with action script ,so that I can control the mask.
Thank you for reading
RW