title: Running total using two columns
body: <p>Given a table with data like:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th><strong>A</strong></th>
  <th><strong>B</strong></th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>Qty.</td>
  <td>Running Total</td>
  </tr>
  <tr>
  <td>5</td>
  <td>5</td>
  </tr>
  <tr>
  <td>5</td>
  <td>10</td>
  </tr>
  <tr>
  <td>5</td>
  <td>15</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I can create the running total using the formula <code>=SUM($A$2:A2)</code> and then drag down to get the running total after each quantity (here Qty.)</p>
  <p><strong>What may I do for calculating running total using two columns which may or may not be consecutive</strong> as shown below:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th><strong>A</strong></th>
  <th><strong>B</strong></th>
  <th><strong>C</strong></th>
  <th><strong>D</strong></th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>Qty. 1</td>
  <td>Other</td>
  <td>Qty. 2</td>
  <td>RT</td>
  </tr>
  <tr>
  <td>2</td>
  <td>blah</td>
  <td>2</td>
  <td>4</td>
  </tr>
  <tr>
  <td>2</td>
  <td>phew</td>
  <td>2</td>
  <td>8</td>
  </tr>
  <tr>
  <td>3</td>
  <td>xyz</td>
  <td>2</td>
  <td>13</td>
  </tr>
  </tbody>
  </table>
  </div>