Problem using string to store evt.target.data and apply property filters

Question

I have about 9 buttons on my stage and I want to write code for the rollover and rollout effects, I only want to write the code once so I am trying to pass the button info into a string via evt.target.data and it pass the info properly into my string variable but when I try to set my filter to that variable, setting my movieclip instance name to that variable, I get 2 errors:
1119: Access of possibly undefined property filters through a reference with static type String.
Warning: 1072: Migration issue: String is not a dynamic class.  Instances cannot have members added to them dynamically.
My code is:
import fl.transitions.Tween;
import fl.transitions.easing.*;
var thumbArray:Array=new Array();
var movieClipLoader:Loader;
var movieClipsStage:Array=new Array(mc0,mc1,mc2,mc3,mc4,mc5,mc6,mc7,mc8);
toolTip_mc.alpha=0;
var lumRd:Number=.2127;
var lumGr:Number=.7152;
var lumBl:Number=.0722;
//grayscale
var grayscale:ColorMatrixFilter = new ColorMatrixFilter([lumRd, lumGr, lumBl, 0, 0,
lumRd, lumGr, lumBl, 0, 0,
lumRd, lumGr, lumBl, 0, 0,
0, 0, 0, 1, 0]);
//drop shadow
var ds:DropShadowFilter = new DropShadowFilter();
ds.distance=5;
ds.blurX=10;
ds.blurY=10;
ds.alpha=.7;
//varialbe to store movieclips based on rollover
var whichThumb:String;
var myXMLInfo:XML;
var thumbList:XMLList;
var toolNameList:XMLList;
var myXMLLoader:URLLoader=new URLLoader  ;
myXMLLoader.load(new URLRequest("stars.xml"));
myXMLLoader.addEventListener(Event.COMPLETE, loadComplete);
function loadComplete(evt:Event):void {
myXMLLoader.removeEventListener(Event.COMPLETE, loadComplete);
myXMLInfo=XML(evt.target.data);
thumbList= new XMLList();
toolNameList=myXMLInfo.star.@toolname;
thumbList=myXMLInfo.star.@thumbimage;
for (var n:int=0; n<movieClipsStage.length; n++) {
movieClipLoader=new Loader();
movieClipLoader.load(new URLRequest(thumbList[n]));
movieClipsStage[n].addChild(movieClipLoader);
mc0.filters=mc1.filters=mc2.filters=mc3.filters=mc4.filters=mc5.filters=mc6.filters=mc7.fi lters=mc8.filters=[ds,grayscale];
mc0_bu.addEventListener(MouseEvent.ROLL_OVER, thumbRollEffect);
function thumbRollEffect(evt:MouseEvent):void {
whichThumb = evt.target.name;
whichThumb.filters=[ds];
Thank you for your help!

Answer 1

kglad, thanks for helping.
basically, i am a newbie and i'm not clear on your answer . if evt.currentTarget is better, I would like to use the best method, so thanks. i'm trying to get my head around what's going on here in the code. i get that actionscript is storing a "reference" to the object but I don't get why I can't put that reference (which is the name of the movieclip on the stage I wish to apply filters to, i.e. mc0) into a string variable (whichThumb) and then use that string variable to apply the filter (whichThumb.filters=[ds];)
on one hand, i'm getting error that says "possibly undefined property filters thru a ref with string" which I don't get because the filters are defined outside of the function and are called intially in the load function with no problem. and on the other hand, i am getting another error saying there is a "migraiton issue" with my string not being a dynamic class. do i need to make the var whichThumb another type other than string? if so, what type. maybe that will also solve the "undefined property" issue as well.
still learning, Thanks for help!