Bootstrap form example

HTML

<link rel="stylesheet" href="http://netdna.bootstrapcdn.com/bootstrap/3.0.1/css/bootstrap.min.css">
<div class="btn-group">
  <button type="button" class="btn btn-default">Left</button>
  <button type="button" class="btn btn-default">Middle</button>
  <button type="button" class="btn btn-default">Right</button>
</div>

CSS

body{margin:10px}
.btn-group > .btn.btn-default.radius-left {
    border-top-left-radius: 4px!important;
    border-bottom-left-radius: 4px!important;
}
.btn-group > .btn.btn-default.radius-right {
    border-top-right-radius: 4px!important;
    border-bottom-right-radius: 4px!important;
}

JavaScript

$("button:eq(2)").hide();
$(".btn-group button:visible").first().addClass('radius-left').end().last().addClass('radius-right');