<script type="text/javascript">
function checkForm(form)
{
    if( !confirm('Are you sure you want to do this?') )
    {
        return false;
    }

    if( !form.Subject.value )
    {
        alert("Subject is Required");
        return false;
    }


    if( !form.Text.value && !form.HTML.value )
    {
        alert("Text or HTML is Required");
        return false;
    }
}

<?PHP
if( $bulk )
{
?>

window.open('admin.php?Run=StartBulkEmail', '_blank', 'menubar=no,height=150,width=450,scrollbars=yes,top=300,left=300');

<?PHP
}
?>
</script>
<form name="form" action="admin.php" target="main" method="post" onSubmit="return checkForm(this)">

<table>
<tr>
<td>
E-mail Members
</td>
</tr>

<tr>
<td>
<b>Sending To</b>
</td>
</tr>
<tr>
<td>
<div>
<?PHP

if( is_array($_REQUEST['Username']) )
{
     echo join(', ', $_REQUEST['Username']);

     foreach($_REQUEST['Username'] as $username)
     {
        echo "<input type=\"hidden\" name=\"Username[]\" value=\"$username\">\n";
     }
}
else
{
    echo "All Members";
}

?>

</td>
</tr>

<tr>
<td>
<b>Subject</b><br />
</td>
</tr>
<tr>
<td>
<input type="text" name="Subject" size="70">
</td>
</tr>

<tr>
<td>
<b>Text</b><br />
</td>
</tr>
<tr>
<td>
<textarea name="Text" cols="60" rows="15" wrap="off"></textarea>
</td>
</tr>

<tr>
<td>
<b>HTML</b><br />
</td>
</tr>
<tr>
<td>
<textarea name="HTML" cols="60" rows="15" wrap="off"></textarea>
</td>
</tr>

<tr>
<td>
<input type="submit" value="Send E-mail">
</td>
</tr>

</table>

<input type="hidden" name="Run" value="EmailMember">

</form>