public function setTextFormat(format:TextLayoutFormat, begin:int, end:int):void{

            var selection:SelectionState = new SelectionState(this._textFlow, begin, end, this._normalFormat);
            IEditManager(_textFlow.interactionManager).applyLeafFormat(format, selection);

        }

for each (var id:String in ids) {
    var element:SpanElement = _textFlow.getElementByID(id) as SpanElement;
    if (element) {
        element.format = getAppropriateFormatForElement(element);
    }
}
_textFlow.flowComposer.updateAllControllers();