function getHTTPObject(){
      if (window.ActiveXObject) return new ActiveXObject("Microsoft.XMLHTTP");
      else if (window.XMLHttpRequest) return new XMLHttpRequest();
      else {
      	alert("Your browser does not support AJAX.");
      	return null;
      }
     }  
     
     function setCost(){
      if(httpObject.readyState == 4){
      	document.getElementById("costtext").value = httpObject.responseText;
      }
     }
     
     function GetCost(){
      httpObject = getHTTPObject();
      if (httpObject != null) {
      	httpObject.open("GET", "costs.php?getcost="
      	+document.getElementById("fromid").value, true);
      	httpObject.send(null);
      	httpObject.onreadystatechange = setCost;
      }
     }

     var httpObject = null;