javascript not working

<script type="text/javascript" language="javascript">
       function SetDate(dateValue) {
           // retrieve from the querystring the value of the Ctl param,
           // that is the name of the input control on the parent form
           // that the user want to set with the clicked date
           ctl = window.location.search.substr(1).substring(4);
           // set the value of that control with the passed date
           thisForm = window.opener.document.forms[0].elements[ctl].value = dateValue;
           // close this popup
           self.close();
       }