[Javascript] check checkboxes in <fieldset>

[Michael Borchers]

<fieldset id="usersGroups[3]">
<legend>Programmierung</legend>
<table width"100%" cellpadding="2" cellspacing="0" border="0">
  <tr>    <td><input type="checkbox" name="users_id[7]" value="22" 
onclick="usersIdCheckboxSelect(this)">A</td>
    <td><input type="checkbox" name="users_id[8]" value="32" 
onclick="usersIdCheckboxSelect(this)">B</td>
  </tr>
  <tr>
    <td><input type="checkbox" name="users_id[9]" value="40" 
onclick="usersIdCheckboxSelect(this)">C</td>
  </tr>
</table>
</fieldset>i need a function to get (later check) all checkboxes within a 
fieldset with a certain ID,in this case usersGroups[3], other fieldsets will 
follow.how can i get the elements?