Prototype align 5 diff mc's / swf's

Hello ive made 5 diff codes to give the right positions on my mc’s.
but the code is all hanging on the mc’s.
Now i was thinking 2 put all code into 1 keyframe.
So i think i need to write a prototype of it.

It will be great if somebody can help me out so i can understand more about how 2 write my own prototype for this.
The file is just for study for me to play a bit with aligning mc’s on stage.

The code that is hanging on the clips are:

Top left


  this._x = (Stage.width - 780)/2;
  this._y = (Stage.height - 570)/2;
  

Top right


  this._x = (Stage.width - this._width);
  this._y = (Stage.height - 570)/2;
  

Center


  this._x = (Stage.width - this._width)/2;
  this._y = (Stage.height - this._height)/2;
  

Bottom right


  this._x = (Stage.width - this._width);
  this._y = (Stage.height - this._height); 
  

Bottom Left


  this._x = (Stage.width - 780)/2;
  this._y = (Stage.height - this._height);
  

My 2nd Q = is there any posibillity to give mc’s or swf’s of a width in %?
For example, 2 load 5 diff mc’s or swf’s with 20% so i got a total of 100%
or 4 of 25%.