function setColumn($firstcol, $lastcol, $width, $format = null, $hidden = 0, $level = 0)
    {
        $this->_colinfo[] = array($firstcol, $lastcol, $width, $format, $hidden, $level);

        // Set width to zero if column is hidden
        $width = ($hidden) ? 0 : $width;

        for ($col = $firstcol; $col <= $lastcol; $col++) {
            $this->col_sizes[$col] = $width;
        }
    }