FieldSet and template views

I am a little bit lost : I am trying to customize a view in drupal 5.7.

I would like my data to be organised in separate fieldsets. To do that, i've used the theme wizard, I have generated the code for the function, something as

function phptemplate_views_view_list_my_view_with_fieldsets($view, $nodes, $type) {

// ...***************************
// ... some code to generate the $items variable
// ... ***************************

$fieldset0 = array(
'#title' => 'Mon title 1',
'#collapsible' => TRUE,
'#collapsed' => FALSE,
'#value' => theme('item_list', $items));

$fieldset1 = array(
'#title' => 'Mon title 2',
'#collapsible' => TRUE,
'#collapsed' => TRUE,
'#value' => theme('item_list', $items));

return theme('fieldset', $fieldset1, $fieldset2);

}

I would like the function to return the multiple fieldset i have generated. What I am missing?