style htmlText in as3?

Hi, I am looking for help and to be pointed to a good place to learn actionscript 3. I am new to flash and actionscript is proving to be very difficult to understand. I do not know the best method to do what i want or the order code needs to be in.  I have several buttons that when clicked show text in a dynamic text box. I want to style part of the text bold, some of it a different font size and change it's leading. I had help with the code i have already. So far the code works great and makes sense to me but I don't know where to go from here. I have spent over a week trying to figure this out- already checked the flash help files but need more step by step help i think. I've been told i should do a stylesheet but i have no idea how to do that either- like i said completely new to this. At this point i am so frustrated and would love to know the correct code to use. Here is everthing in my actions window:

var green_btnInfo = "I want this line to be bold and 14pt<br/>This line should also be bold and 14pt<br/>This line should be regular and 10pt and i want to control it's leading";

green_btn.addEventListener(MouseEvent.CLICK, showInfo);

function showInfo(evt:MouseEvent):void
{
    textBox.htmlText = this[evt.currentTarget.name + "Info"];
}

i did find this http://learnola.com/2008/12/03/actionscript-3-tutorial-using-html-and-css/ but it doesn't match anything i have so not sure what method to use.