我也不知道行不行,可以试试~~~
<script language="JavaScript">
   function check() {
     var pifqy=document.form.pifqy.value;
     if((pifqy==null)||(pifqy.length==0))
     {
           window.open("../qiye/vie_pfqy_search.asp?pifqy="+inputform.pifqy.value ,'JavaScriptIt','toolbar= 0,location= 0,directories= 0,status= 0,menubar= 0,scrollbars= 1,resizable= 1,copyhistory= 1,width=680,height=418');
       return false;
     }
</script>
...
<form  name="inputform" method="post" action="chanp_mingx_add.asp onSubmit="return check()">
...