Word Square Actionscript 3.0 - loops

Question

Using the letters of the word the user inputs, I want to print a square by shifting the letters of the word to the left one position on each line.For example, since COMPUTERS has nine letters, its square will be nine characters across by nine characters down. In each row, each character will be shifted to the end. However, the following program only does one iteration. Please advise. Thanks!
btnDetermine.addEventListener(MouseEvent.CLICK, displayVowels);
function displayVowels(e: MouseEvent): void {
var str1:String;
var str2:String = "";
var i:Number;
str1 = String(txtinString.text);
i=0;
for (i=0; i<str1.length;i++){
str2 = str2 + str1.charAt(i);
}
str2 = str2 + str1.charAt();
lblString.text += str1.charAt(i) + "\r" + str2 ;
}

Answer 1

function displayVowels(e:MouseEvent):void {
//defines your original string
var myString:String = String(txtinString.text);
//the total character length of the original text, determine how many lines to print
var tLength:int = myString.length;
//clears out the textfield in case theres already something on it
lblString.text = "";
//print the first line
lblString.appendText(myString);
//this loops through every line except line1, we printed line1 above
//thus tLength - 1
for (var line:uint = 0; line < tLength - 1; line++) {
//line break
lblString.appendText("\n");
//shift the characters
myString = shiftChar(myString);
//print the result into the textfield
//use appendText instead of textfield += "new text'
lblString.appendText(myString);
}
}
function shiftChar(_myString:String):String {
//save the char at the front, add it to the back later
var offset:String = _myString.charAt(0);
//slice the original string so that the first char is now removed
_myString = _myString.slice(1, _myString.length);
//add the first char of the original string to the back
_myString = _myString + offset;
//return the final results
return _myString;
}