Form-check with Javascript

Hi,
my question: How can I check with Javascript if an fckeditor-instance is filled after sending a form?

The Form:

<form action = '<?php $PHP_SELF ?>' method = 'post' name='formular'>

<tr>
<td class='head' colspan='2'>

      <p class='head'><?=$head?></p>

</td>
</tr>
<tr>
<td class='space' colspan='2'>
<div></div>
</td>
</tr>
<tr><td class='rahmen'><div class='text_bold'>berschrift: </td><td class='rahmen'><textarea rows='3' cols='50' name='ueberschrift'></textarea></div></td></tr>
<tr><td class='rahmen'><div class='text_bold'>Punkt1: </td><td class='rahmen'>
<input type='text' name='punt1'>

<?php
$oFCKeditor = new FCKeditor ;
$oFCKeditor->ToolbarSet = 'Accessibility' ;
$oFCKeditor->CanUpload = false ;    // Overrides fck_config.js default configuration
$oFCKeditor->CanBrowse = false ;    // Overrides fck_config.js default configuration
$oFCKeditor->CreateFCKeditor( 'nachricht', '100%', 150 ) ;
?>  

</div></td></tr>

I've tried these versions:
if (document.formular.nachricht.value.length!=0) {
alert("Bitte fllen Sie das Feld Punkt1 aus!");
return (false);
} //if

if (Window.frames[0].objContent.DOM.body.innerText.length==0) {
alert("Bitte fllen Sie das Feld Punkt1 aus!");
return (false);
} //if

But this didn't work.

Your help is welcome.
Best regards,
Thorsten