Left and right margin on a table row

How can I set the left and right margin of a table row (or something similar to achieve the same result)? I tried border-collapse:separate; border-spacing:20px; but that removed the rows border bottom.

This is what I am trying to create:

Solution

I do not think this is possible with tables.

Here it is with divs and spans. I hope you like it:

<html>
 <head>
  <style>
   div#outer {
    border: 10px solid black;
    width: 30em;
   }
   div#header {
    background-color: red;
    color: white;
    text-align: center;
   }
   div.row {
    border-bottom: 1px dashed red;
    margin: 10px 20px;
    clear: both;
   }
   span.left {
    float: left;
   }
   span.right {
    margin-left: 10em;
   }
  </style>
</head>
 <body>
  <div id="outer">
  <div id="header">Some table head text</div>
   <div class="row">
    <span class="left">Col</span>
    <span class="right">Col</span>
   </div>
   <div class="row">
    <span class="left">Col</span>
    <span class="right">Col</span>
   </div>
   <div class="row">
    <span class="left">Col</span>
    <span class="right">Col</span>
   </div>
  </div>
 </body>
</html>