title: Modify specific cell value using Axlsx gem given the column number and row numer
body: <p>I am trying to use asxlx gem to write an excel sheet but I have failed miserably trying to access individual cell values..</p>
  
  <p>For example for do I get the value of the cell  2 in column 2</p>
  
  <p>How do I change the value of cell 10 in column 19 ??</p>