Scrolling externally loaded dynamic text

Hello,
I have a dynamic text box into which I am loading external XML and a CSS file. I have up and down scroll buttons working that scroll through the text box content. This is what the code looks like so far (there are two text boxes on the stage called varText_txt and bothText_txt:

function textLoader() {
varData = new LoadVars();
varData.onLoad = function() {
varText_txt.html = true;
varText_txt.htmlText = this.myVariable;
};
bothData = new LoadVars();
bothData.onLoad = function() {
bothText_txt.html = true;
bothText_txt.htmlText = this.myBothText;
};
varData.load(“images/claudeText.txt”);
bothData.load(“images/bothText.txt”);
}
var myCSS = new TextField.StyleSheet();
myCSS.load(“myStyle.css”);
myCSS.onLoad = function() {
varText_txt.styleSheet = myCSS;
bothText_txt.styleSheet = myCSS;
textLoader();
};
scrollBtn_up01.onRelease = function(){
bothText_txt.scroll–;
}
scrollBtn_dwn01.onRelease = function(){
bothText_txt.scroll++;
}
scrollBtn_up02.onRelease = function(){
varText_txt.scroll–;
}
scrollBtn_dwn02.onRelease = function(){
varText_txt.scroll++;
}

This is all working great. Now I would like to add a custom draggable scroll bar. Does anyone know how this is done or have sample code that I can pick apart.
Thank you.