[jQuery] How to dynamically size an <li>?

[jQuery] How to dynamically size an <li>?


What I Have:
I have a bunch of inline blocks next to each other like such:
_[A]_[B]_[C] _[D]_
Key:
_ = margin
[letter] = box element, <li> in my case
Question:
How do I make it so that the margins on the left and right side of my
<li>'s determine the <li>'s width? So, in other words, I am looking
for each box element to have a uniform width (so A, B, C, D will all
have the same width value), but I would like the margins to in fact
determine this value...? Basically, I suppose I am more or less
setting barricades outside of the box models (margins) and having the
padding fill-in the remaining amounts, equally for all 4 boxes...
In effect, I would like these <li>'s to stretch the width of a larger
container (box), so that their width value is maximized, but
nonetheless conforms to the margins... Hope this makes sense.
I am new to jQuery, how would I go about coding this up?