Change layout for specified rows

[eluser]Unknown[/eluser]
How can I change the layout of specified rows (not all rows) with the HTML Table Class in CodeIgniter? I tried it with the template array, but this effects the entire table respectively all rows.

Code:

$tmpl = array (
    'table_open'          => '<table border="0" cellpadding="4" cellspacing="0">',
    'heading_row_start'   => '<tr>',
    'heading_row_end'     => '</tr>',
    'heading_cell_start'  => '<th>',
    'heading_cell_end'    => '</th>',
    'row_start'           => '<tr>',
    'row_end'             => '</tr>',
    'cell_start'          => '<td>',
    'cell_end'            => '</td>',
    'row_alt_start'       => '<tr>',
    'row_alt_end'         => '</tr>',
    'cell_alt_start'      => '<td>',
    'cell_alt_end'        => '</td>',
    'table_close'         => '</table>'
);
$this->table->set_template($tmpl);