function deliveryCost (postcode) {
    var i=0;
  document.homepage.dcost.value = "";
  while (i < pcode1.length)
    {
    if (postcode >= pcode1[i] && postcode <= pcode2[i])
        {
         if (dprice[i] == 0)
            {
                document.homepage.dcost.value = "free";
            }
        else
            {
                document.homepage.dcost.value = "$"+floatToTwoDec(dprice[i]);
            }
         }
     i++;
    }
    if (document.homepage.dcost.value == "")
       {alert("Please make sure your postcode is valid.");}
  }