Well, for starters it helps to understand what you are using.
Just do a simple proof of concept and go from there?
Code:
<div id="foo" style="height:10px;overflow:hidden;width:100px;">
<div id="bar" style="position:absolute;top:0px;left:0px;">
text text text text text texttext text texttext text texttext text texttext text texttext text text
</div>
</div>
Then write up some JavaScript code to manipulate the "left" value - see document.getElementById('bar').style.left = x
This is just an idea, or a draft.