--- uc_quote.js (saved version)
+++ (current document)
@@ -47,6 +47,11 @@
 }
 
 function quoteCallback(products){
+  var postalCode = $("input[@name*=delivery_postal_code]").val();
+  if (!postalCode) {
+    return false;
+  }
+  
   var updateCallback = function (progress, status, pb) {
     if (progress == 100) {
       pb.stopMonitoring();