I am looking for a tool very similar to http://www.tothepc.com/archives/combine-merge-multiple-css-files/

However, given this example:

test1.css:

#admin {
    background: #c9d2dc;
    border-color: #ccc
}

test2.css:

#admin {
    background: #222;
    border-bottom: 1px solid #444;
    border-left: 1px solid #444;
    padding: 2px;
    position: fixed;
    right: 0px;
    top: 0px;
    width: 120px;
    z-index: 2
}

It will only allow you to select one or the other. I want to merge them, making it:

#admin {
    background: #c9d2dc;
    border-color: #ccc
    border-bottom: 1px solid #444;
    border-left: 1px solid #444;
    padding: 2px;
    position: fixed;
    right: 0px;
    top: 0px;
    width: 120px;
    z-index: 2
}