Flash - Event on selecting the text

code:

this.onMouseUp = function(){
var beginIndex:Number = Selection.getBeginIndex();
var endIndex = Selection.getEndIndex()
trace("TARGET : " + Selection.getFocus());
trace("Start Index = " + beginIndex + " :: End Index = " + endIndex)
trace("SelectedChar = " +
eval(Selection.getFocus()).text.slice(beginIndex,endIndex));
}