title: Calculate hours outside normal working time
body: <p>From my sample xls(office2007) listed below. I am trying to calculate the hours worked from 17:00 onwards. could someone show me how would I write the formula to achieve this.
  Many thanks...</p>
  
  <pre><code>Leaving Time    Arrival Time    DeliveryTime    RTB      Time per Job   hoursforDaysWork
  09:30:00       11:05:00         11:15:00        11:15:00    01:45:00    12:00:00
  11:15:00        12:15:00        12:30:00        13:30:00    02:15:00    
  13:30:00       15:30:00         15:45:00        15:45:00    02:15:00    
  15:45:00       18:15:00         18:30:00        18:30:00    02:45:00    
  18:30:00       19:00:00         19:45:00        21:30:00    03:00:00    
  </code></pre>