script doesn't run before redirect

I have an ASP page (posting a form to MS Access) and if a condition is not met it pops up a box telling the user that part of the input was invalid and wasn't posted.

works fine

but

I also want to response.redirect the page back to the form. When I do, the script doesn't run - I'm assuming it doesn't have time?

any way to slow down the redirect or force the script to run first?

<%if valid(request.form("ior")) - request.form("baan") < 0 then
%>
<SCRIPT LANGUAGE="JAVASCRIPT">
window.open('invalid.htm', 'invalid', 'width=300,height=300');
</SCRIPT>
<%end if

Could you just add history.go(-1) to your javascript? Not sure that'll keep your form values, but you might try it out.