how do I select a div with class "A" but NOT with class "B"?

I have some divs:

<div class="A">"Target"</div>
<div class="A B">"NotMyTarget"</div>
<div class="A C">"NotMyTarget"</div>
<div class="A D">"NotMyTarget"</div>
<div class="A E">"NotMyTarget"</div>

Is there a CSS selector that will get me the div containing Target but not the divs containing NotMyTarget?

Solution must work on IE7, IE8, Safari, Chrome, and Firefox

Edit: So far Nick is the closest. It's clumsy and I don't like the solution, but at least it works:

.A
{
   /* style that all divs will take */
}
div.B 
{
  /* style that will override style .A */
}