title: Sigma function in excel
body: <p>How can I use sigma with boundaries in excel 2007? For example I want to calculate this value:</p>
  
  <pre><code>sigma [e^(m-n)*i(m)]
  </code></pre>
  
  <p>in which n values are a column starting from 0 to 100 and for each n, m is started from 0 ended to n and i(m) is corresponding value specified in Raw m and form a column.  For example for n=100:</p>
  
  <pre><code>sigma [e^(m-100)*i(m)] and m is 0 to 100.
  </code></pre>
  
  <p>Please don't tell to write for each raw separately and then sum up because for n=1 to 100 I should do this operation for each n, n times which leads to 1+2+3+...+100=100*101/2=5050 times. </p>