The GridCheckBoxColumn in Telerik RadGrid have CheckBox in their cells. They are
not considered as data, that is why when you select the second parameter of the ExportToExcel method to be true, those CheckBoxes will be stripped from the resulting
Excel file. One suggestion will be to use a GridBoundColumn where you can represent the boolean value with a Yes/No. Hide the column in the Grid (setting its Visible property to false), then switch
its visibility with the one for the GridCheckBoxColumn, and finally export it to Excel calling Telerik RadGrid's ExportToExcel
method.