title: How to manipulate the contents of a DB Grid before display?
body: <p>I have a column in a DB table which stores pressure. The pressure is always stored as PSI and can be converted to BAR by diving by 14.5.</p>
  
  <p>The user can toggle display of PSI/BAR with a Radio Group.</p>
  
  <p>I was using a <code>TStringGrid</code> and am converting to a <code>TDbGrid</code> - which is quite new to me. </p>
  
  <p>When the user toggles PSI/BAR, how to I update the display in my DB grid? (I imagine that I just execute it's query again? or Call <code>query.Refresh()</code>?) But how do I do the conversion?</p>
  
  <ol>
  <li>Possibly a stored procedure, although that seems like overkill and stored procedurs are also new to me...</li>
  <li>By changing the <code>SELECT</code> statement of my query? But how would I do that? <code>SELECT pressure / 14.5 FROM measurements</code>? Or how?  </li>
  <li>Or is there an <code>OnBeforeXXX()</code> which I can code? Or <code>OnGetDisplayText()</code> or some such?</li>
  </ol>
  
  <p>I am sure thta this is very basic, but until now I have just been displaying unmanipulated data and now I need a conversion function. Google didn'ty help, but I probably didn't know what to ask for.</p>
  
  <p>I also want to change the text of the column title, toggling between "Presure (PSI)" and "pressure (BAR)".
  Thanks in advance for any help.</p>