Rich Text Editor In Admin CP

[Jafo232]

I have been trying to modify the text area in the "Send Email To Users" feature to make it a rich text area. I see it does not use a template, just this code in email.php:

print_form_header('email', 'dosendmail');
		print_table_header($vbphrase['email_manager']);
		print_yes_no_row($vbphrase['test_email_only'], 'test', 0);
		print_input_row($vbphrase['email_to_send_at_once'], 'perpage', 500);
		print_input_row($vbphrase['from'], 'from', $vbulletin->options['webmasteremail']);
		print_input_row($vbphrase['subject'], 'subject');
		print_textarea_row($vbphrase['message_email'], 'message', '', 10, 50);
		$text = $vbphrase['send'];

What would be the best way to change that?