You can utilize a UIScrollbar component with a textfield.
ok so how do i go about that in cs4? the last one i used was mx and that was a couple years ago
I can't answer that specifically for CS4 because I don't have it. What you would normally do is first create the textfield to the size you want, then drag the scrollbar from the components library and drop it on the desired edge of the textfield (keep trying until it locks /sizes to it).
If you will need to control the scrollbar with code, such as to update() it after dynamically changing the content, then you will need to assign it an instance name.
The Flash help documentation will provide all the information you need to do this... it's where I would be getting the information I'd offer you. The only thing is that CS4 doesn't make easy work of using the help docs.