title: Set style in cxGrid based on data from all rows
body: <p>I have a few grids where users enters from-to dates, and would like to set background colour on rows with date-interval that overlap other rows date-interval.</p>
  
  <p>Now I'm using oncalc event on the dataset to set an overlap-flag, but it is a slow solution, and I like to know if it's solvable in cxGrid instead.</p>
  
  <p>Ove B-)</p>