Theming php snippet

http://drupal.org/node/63422

I've used the above snippet to display all users belonging to a certain role.
The user names are longer than the width of the resulting table. Making the table bigger doesn't change a thing because the actual data that goes in the table is cut off like "username..."

Guess i need to change the following code

$output .= theme('table', $header, $rows);
$output .= theme('pager', NULL, 50, 0);

to look like

$output .= theme('wide_table', $header, $rows);
$output .= theme('pager', NULL, 50, 0);

and somehow create a new wide_table function that does the exact same thig but creates an auto-width table.
Anyone got any ideas as where i'm suppossed to find these "theme" functions??