Variable Reference of Instance Name

Question

While I have had no problems with bracket evaluation of
constants and number variables, I don't know the coding convention
for brack evaluation of a string.
I get an undefined for oBtnName
oBtnName = new Object;
oBtnName = this["mcWing" + aWingColor[nIdx] + "Btn"];
where aWingColor is an array of strings. So I tried setting
aWingColor[nIdx] to variable thinking the inside array brackets
were goofing this up:
oBtnName = new Object;
var sWingColor:String = aWingColor[nIdx];
oBtnName = this["mcWing" + sWingColor + "Btn"];
trace (sWingColor + " " + oBtnName._name );
returns Pink undefined
and interactive debug is showing oBtnName as undefined as
well.
So, then I tried this
oBtnName = this["mcWing" + sWingColor._value + "Btn"];
and then this
oBtnName = this["mcWing" + "[sWingColor]" + "Btn"];
and so on and so on. . . .

Answer 1

Isn't
this["mcWing" + aWingColor[nIdx] + "Btn"]=new Object()
the same as
var oBtnName:Object = new Object;
oBtnName = this["mcWing" + aWingColor[nWingRollIdx] + "Btn"];
I am doing this to shorten the reference name
Here is the rest of the code
mcWingPinkBtn.onRollOut = function () {
clearInterval(nInterval);
nWingRollIdx = 1;
nInterval = setInterval(fFadeOutWing, 1);
function fFadeOutWing():Void {
var oBtnName:Object = new Object;
oBtnName = this["mcWing" + aWingColor[nWingRollIdx] +
"Btn"];
oBtnName._alpha -= nAlphaIncrement;
----oBtnName is undefined here so the following if doesn't
work -----
if(oBtnName._alpha <= nAlphaStart) {
oBtnName._alpha = nAlphaStart;
clearInterval(nInterval);
updateAfterEvent();