title: Count expression in SSRS 2008
body: <p>I have a situation where I have a column name `NotifcationLog.Status.</p>
  
  <p>The status can be of 3 types Accepted, Pending &amp; Overdue. I need to have a count of all the Notifications status . </p>
  
  <p>I created a calculated field with the following expression </p>
  
  <pre><code>=COUNT(IIF(Fields!NotificationStatus.Value="Accepted",1,Nothing))
  </code></pre>
  
  <p>When I tried to add this Calculated field to the table and preview it , I got a error stating "aggregate ,row number,running value,previous and lookup functions cannot be used in calculated field expressions "</p>
  
  <p>What should i do now ??</p>