QF - conditional elements requiring conditional rules!

Hi I have the following form fields generated by QuickForm: <select onchange="this.form.url_manual.disabled=this.selectedIndex!=0;" name="url_automatic">

    <option value="none">Ekstern side</option>
    <option value="url1">Link to URL1</option>
    <option value="url2">Link to URL2</option>
    <option value="url3">Link to URL3</option>

</select> <input value="Type URL" onchange="this.form.url_automatic.disabled=(this.value!='' && this.value!=this.defaultValue);" name="url_manual" type="text" /> These two fields are mutually exclusive meaning that either you choose an option from the drop-down menu or you type in a value in the text field. Now I want to add a crude validation to the text field helping the user to type in a correct URL and I've reached the following: $form->registerRule('url', 'regex', '/(^(ldap|http|https|ftp):\/\/(([a-z0-9\-\.]+\.+[a-z]{2,6})|([0-9]{1,3}\.){4})(\]?)$)/'); But the problem is that an URL is ONLY required IF the first/default option from the drop-down menu is active - if any other element is chosen, the text field is disabled and the rule shouldn't trigger! How can I accomplish this behaviour using QuickForm? Regards, Tommy Ipsen