title: SSRS: How to show a percentage of overall total in a group header
body: <p>I have a report that shows customer appointments, by sales rep for the past 3 months grouped by customer sector.  In the Customer Sector group header, I want to show the percentage of the overall total of customers in this sector that the appointments represent.</p>
  
  <p>For example, my report shows that 6 appointments were made by John Smith for customers in the 'Defence' sector in the past 3 months.  John Smith also made 4 appointments for customers in the 'Local Government' sector.  </p>
  
  <p>I know that I have a total of 10 Defence customers and 20 Local Government customers.  How can I show the percentage of customers seen in that sector in the past three months?</p>
  
  <p>So I currently show:</p>
  
  <pre><code>Sales Rep: John Smith (10 appointments)
       Sector: Defence (2 customers)
            Customer 1 (4 appointments)
                  Appointment 1 -- Blah
                  Appointment 2 -- Blah
                  Appointment 3 -- Blah
                  Appointment 4 -- Blah
            Customer 2 (2 appointments)
                  Appointment 1 -- Blah
                  Appointment 2 -- Blah
       Sector: Local Government (2 customers)
            Customer 3 (3 appointments)
                  Appointment 1 -- Blah
                  Appointment 2 -- Blah
                  Appointment 3 -- Blah
            Customer 4 (1 appointment)
                  Appointment 1 -- Blah
  </code></pre>
  
  <p>And I want to show:</p>
  
  <pre><code>Sales Rep: John Smith (10 appointments)
       Sector: Defence (2 customers - **20% of total Defence customers**)
            Customer 1 (4 appointments)
                  Appointment 1 -- Blah
                  Appointment 2 -- Blah
                  Appointment 3 -- Blah
                  Appointment 4 -- Blah
            Customer 2 (2 appointments)
                  Appointment 1 -- Blah
                  Appointment 2 -- Blah
       Sector: Local Government (2 customers - **10% of Local Government customers**)
            Customer 3 (3 appointments)
                  Appointment 1 -- Blah
                  Appointment 2 -- Blah
                  Appointment 3 -- Blah
            Customer 4 (1 appointment)
                  Appointment 1 -- Blah
  </code></pre>
  
  <p>I'm a SSRS noob, so don't know how I can achieve this.  Do I add a dataset to the report that has the total number of customers in each customer sector?</p>
  
  <p>If I do that, how can I use the total for say, Defence, in the expression I currently show in the Customer Sector group header to work out the percentage of total customers seen in that sector?</p>
  
  <p>Due to database restrictions, I can't create any tables, views or stored procs in the source database, so all the work has to be done in the report.</p>
  
  <p>I'm using SSRS 2005.</p>
  
  <p>Many thanks!</p>