contact form- how to redirect on submit

[ackg37]

I have a functioning contact form. I want to add a redirect; right now it automatically redirects to the index page. However, the 'onsubmit' attribute is already being used to validate the form. I can't alter the php script the form uses, so have to do all this from my end. How else could I keep form validation or tell it where to redirect on submission? The code is included below. 

Thanks!

 

In the head: 

<script type="text/javascript">
function checkForm(frm){
msg = "";
   if(!frm.name.value){
      msg += "- Name is required\n";
   }
   if(!frm.email.value){
      msg += "- Address is required\n";
   }
   if(!frm.location.value){
      msg += "- Email is required\n";
   }
   if(!frm.schedule.value){
      msg += "- Email is required\n";
   }
   if(!frm.likes.value){
      msg += "- Email is required\n";
   }
   if(!frm.dislikes.value){
      msg += "- Email is required\n";
   }
   if(msg != ""){
      alert(msg);
      return false;
   }
}
</script> 

 

In the table: 

<form action="/webformmailer.php" method="post" onsubmit="return validate_form(this)>
    input type=hidden name="required" value="email,phone">