<?php
if(isset($_COOKIE['cookie_name_here'])){
//Cookie is set
require_once("page_a.php");
}else{
//Cookie wasn't set
require_once("page_b.php");
}
?>
It's just a simple cookie check - you don't need a plugin either. Just hard-code it into your theme.
Code:<?php if(isset($_COOKIE['cookie_name_here'])){ //Cookie is set require_once("page_a.php"); }else{ //Cookie wasn't set require_once("page_b.php"); } ?>