Popup vindue hver 20 min?

Er det muligt at lave dette script om så popup vinduet kommer igen efter 20 min?

<script language="JavaScript">
<!--
var expDays = 1; // number of days the cookie should last

var page = "poll.php";
var windowprops = "width=400,height=225,location=no,toolbar=no,menubar=no,scrollbars=no,resizable=yes";

function GetCookie (name) { 
var arg = name + "="; 
var alen = arg.length; 
var clen = document.cookie.length; 
var i = 0; 
while (i < clen) {   
var j = i + alen;   
if (document.cookie.substring(i, j) == arg)     
return getCookieVal (j);   
i = document.cookie.indexOf(" ", i) + 1;   
if (i == 0) break; 
} 
return null;
}
function SetCookie (name, value) { 
var argv = SetCookie.arguments; 
var argc = SetCookie.arguments.length; 
var expires = (argc > 2) ? argv[2] : null; 
var path = (argc > 3) ? argv[3] : null; 
var domain = (argc > 4) ? argv[4] : null; 
var secure = (argc > 5) ? argv[5] : false; 
document.cookie = name + "=" + escape (value) +
((expires == null) ? "" : ("; expires=" + expires.toGMTString())) +
((path == null) ? "" : ("; path=" + path)) + 
((domain == null) ? "" : ("; domain=" + domain)) +   
((secure == true) ? "; secure" : "");
}
function DeleteCookie (name) { 
var exp = new Date(); 
exp.setTime (exp.getTime() - 1); 
var cval = GetCookie (name); 
document.cookie = name + "=" + cval + "; expires=" + exp.toGMTString();
}
var exp = new Date();
exp.setTime(exp.getTime() + (expDays*24*60*60*1000));
function amt(){
var count = GetCookie('count')
if(count == null) {
SetCookie('count','1')
return 1
}
else {
var newcount = parseInt(count) + 1;
DeleteCookie('count')
SetCookie('count',newcount,exp)
return count
  }
}
function getCookieVal(offset) {
var endstr = document.cookie.indexOf (";", offset);
if (endstr == -1)
endstr = document.cookie.length;
return unescape(document.cookie.substring(offset, endstr));
}

function checkCount() {
var count = GetCookie('count');
if (count == null) {
count=1;
SetCookie('count', count, exp);

window.open(page, "", windowprops);

}
else {
count++;
SetCookie('count', count, exp);
  }
}
// -->
</script>