title: Format cell when exporting to Excel
body: <p>I want to format certain cell values when right clicking the grid and choosing Export to Excel. I assume I'm going to use the <code>processCellCallback</code> function but how do I call it or override it?</p>
  
  <p>I found the export function here <code>this.gridOptions.api.exportDataAsExcel</code> but I'm not sure how to connect the two, and I can't find any good examples at the <a href="https://www.ag-grid.com/javascript-grid-export/" rel="nofollow noreferrer">ag-grid documentation</a>.</p>
  
  <p>This is what I've tried:</p>
  
  <pre><code>this.gridOptions = &lt;GridOptions&gt;{
      columnDefs: [{
          // Here are my column definitions
      }],
      processCellCallback: function (params) {
          console.log(params)
          if (params.column.getColId() === 'Created' &amp;&amp; params.value) {
              return this.toDateTime(params.value);
          } else {
              return params.value;
          }
      }
  }
  </code></pre>