How to display an angled border around a group of elements?

How to display an angled border around a group of elements?

Not too sure if I can even do this with just CSS but here goes:
I want to use the border property (or similar) to display an angled border
around a group of elements. I suppose the best way to explain is just to
show you:
HTML:
<ul>
<li>link</li>
<li>link</li>
<li>link</li>
</ul>
CSS:
li {
border-top:1px solid black;
border-bottom:1px solid black;
border-right: /* ??? */ ;
}
Looks Like:
-----------------\
link \
-------------------\
link \
---------------------\
link \
-----------------------\
Preview:
As far as I know plain css can't do this. What about canvas or jQuery?
Would there be something I could use there to help?