$description = new HtmlEditorField('Description');
$description->setRows(10);
$fields = new FieldList(new TextField('Title', 'Job Title'),
                  new TextField('JobType','Type'),
                  new DateField('ClosingDate','Closing Date'),
                  new TextField('Reference'),
                  new TextField('ContactName','Contact'),
                  new EmailField('ContactEmail','Email'),
                  $description);

class JobVacancy extends DataObject
{
static $db = array(
      'Title' => 'Text',
      'JobType' => 'Text',
      'ClosingDate' => 'Date',
      'Reference' => 'Text',
      'ContactName' => 'Text',
      'ContactEmail' => 'Text',
      'Description' => 'HTMLText'
);
}

<div id="Description" class="field htmleditor">
   <label class="left" for="Form_CreateVacancyForm_Description">Description</label>
   <div class="middleColumn">
      <textarea name="Description" value="" class="htmleditor" id="Form_CreateVacancyForm_Description" rows="10" cols="10" tinymce="true" style="width: 97%; height: 160px"></textarea>
   </div>
</div>

</div>
<script type="text/javascript" src="/tamsec.com.au/framework/thirdparty/tinymce/tiny_mce_gzip.php?m=1348579864&js=1&amp;plugins=contextmenu,table,emotions,paste,spellchecker&amp;themes=advanced&amp;diskcache=true&amp;src=false"></script>
<script type="text/javascript" src="/tamsec.com.au/framework/thirdparty/jquery/jquery.js?m=1348579864"></script>
<script type="text/javascript" src="/tamsec.com.au/framework/thirdparty/jquery-ui/jquery-ui.js?m=1348579860"></script>
<script type="text/javascript" src="/tamsec.com.au/framework/javascript/DateField.js?m=1348579851"></script>
<script type="text/javascript">//<![CDATA[
if((typeof tinyMCE != 'undefined')) {
var ssTinyMceConfig = {"friendly_name":"(Please set a friendly name for this config)","priority":0,"mode":"specific_textareas","editor_selector":"htmleditor","width":"100%","auto_resize":false,"theme":"advanced","theme_advanced_layout_manager":"SimpleLayout","theme_advanced_toolbar_location":"top","theme_advanced_toolbar_align":"left","theme_advanced_toolbar_parent":"right","blockquote_clear_tag":"p","table_inline_editing":true,"safari_warning":false,"relative_urls":true,"verify_html":true,"plugins":"contextmenu,table,emotions,paste,spellchecker","theme_advanced_buttons1":"bold,italic,underline,strikethrough,separator,justifyleft,justifycenter,justifyright,justifyfull,formatselect,separator,bullist,numlist,outdent,indent,blockquote,hr,charmap","theme_advanced_buttons2":"undo,redo,separator,cut,copy,paste,pastetext,pasteword,spellchecker,separator,advcode,search,replace,selectall,visualaid,separator,tablecontrols","theme_advanced_buttons3":""};
}
//]]></script></body>
</html>