title: Get the average monthly value from 2 SP List columns and display in new column
body: <p>I need to calculate the average value for each month. Currently I have 2 columns "DATE" (date value e.g 01/01/2010) and AccOpen (number value). So for all dates within January I need to return the average value of all numbers contained in the corresponding AccOpen rows for January dates.</p>
  
  <p>Is it possible to use the <strong>CALCULATED</strong> option and input a <strong>FORMULA</strong> that will return the average for all itmes within each months period (when adding a column to the list ?</p>
  
  <p>DATE    ACCOPEN AVERAGE
  01/01/2010  2   2
  02/01/2010  2<br>
  03/01/2010  2<br>
  04/01/2010  2<br>
  01/02/2010  2   2
  02/02/2010  2<br>
  03/02/2010  2<br>
  04/02/2010  2   </p>