Dynamically Changing A Stylesheet

I have a piece of javascript I need to modify. Right now it changes a stylesheet in the document between style.css and no_indent.css. These
are in the head of my document:

<link rel=stylesheet href=/style.css>
<link rel=stylesheet href=/no_indent.css>
<link rel=stylesheet href=/style.css>

What the code below does is toggle between the two depending on what link is clicked. Here are the links:

<a href=javascript:changeSheets(1)>Threaded</a>
<a href=javascript:changeSheets(2)>Flat</a>

What I want to do is have one link that will toggle between the two
stylesheets. So the page loads style.css initially. If the link is
clicked once it changes to no_indent.css. If it's clicked again it
changes back to style.css, and so on.

Can anyone let me know how to do this?

code:
----------------------------------

function changeSheets(whichSheet){
whichSheet=whichSheet-1;
if(document.styleSheets){
var c=document.styleSheets.length;
for(var i=0;i<c;i++){
if(i!=whichSheet){
document.styleSheets[i].disabled=true;
}else{
document.styleSheets[i].disabled=false;
}
}
}
}