function IsEmpty(aTextField) {
   if ((aTextField.value.length==0) ||
   (aTextField.value==null)) {
      return true;
   }
   else { return false; }
}

function ValidateForm(form)
{
	//mytext = document.getElementById(txt);
  if(IsEmpty(form.topic)) 
  { 
     alert('You need to enter a topic') 
     form.topic.focus(); 
     return false; 
  } 
	return true;
 }