title: Conditional Formatting with Custom Formula referencing the cell itself
body: <p>I have a google spreadsheet which has columns for each day (with the date in the top cell) and in each cell a string indicating status.</p>
  
  <p>I need to apply conditional formatting to cells based on the criteria of the date of the column being in the past AND the text inside the cell starting with the substring "OK".</p>
  
  <p>It seems that I must use a Custom Formula in order to deal with the date part, but then how would I reference the content of the cell itself? I've tried referencing the cell using <code>CELL("contents",ADDRESS(ROW(),COLUMN())</code> but this returns an <code>Error: Argument must be a range</code>.</p>