title: running sum & add value to first row only
body: <p>I am creating a ledger using MS Access 2010</p>
  
  <p>I have the ledger report with unbound textbox to calculate the balance of each record include running sum for a calculation of 2 fields as below:</p>
  
  <blockquote>
    <p>[Debit] - [credit]</p>
  </blockquote>
  
  <p>It's working good, what I want to do is to add the open account value to the 1st row only, so the calculation for the 1st row only should be like this</p>
  
  <blockquote>
    <p>[Debit] - [credit] + OpenBalance</p>
  </blockquote>
  
  <p>then to use the 1st calculation for the other rows</p>
  
  <p>but I failed to do it, any idea of how to achieve this?</p>