[F8] Adding text before and after selected text in textbox

[Vexy]

hi.. I have really no idea how to do this, but i have a textbox and a button.
When this button is clicked, i want it to add "<b>" before the currently selected text in the textbox. How would i go by this?
Thanks

[Vexy]

inputText.onKillFocus = function() {
_root.onEnterFrame = null;
trace(this.text.substr(this.selected_text.split(",")[0], this.selected_text.split(",")[1]));
inputText.setTextFormat(this.selected_text.split(",")[0], this.selected_text.split(",")[1], myTextFormat);
};
var newTextFormat = new TextFormat();
newTextFormat.bold = true;
inputText.onSetFocus = function() {
setBold.onRelease = function() {
begin = Selection.getBeginIndex();
end = Selection.getEndIndex();
inputText.setTextFormat(begin,end,newTextFormat);
trace(begin);
trace(end);
};
}; 

I have something of a test here to see if i could add Bold to the selected text. But cant even get that working