function isNumeric(strString)
   //  check for valid numeric strings	
   {
   var strValidChars = "0123456789.-";
   var strChar;
   var blnResult = true;

   if (strString.length == 0) return false;

   //  test strString consists of valid characters listed above
   for (i = 0; i < strString.length && blnResult == true; i++)
      {
      strChar = strString.charAt(i);
      if (strValidChars.indexOf(strChar) == -1)
         {
         blnResult = false;
         }
      }
   return blnResult;
   }

function calculate(mykey)
	{
	// check div exists
	if (document.getElementById('mortgageValue'))
		{
		// init var
		var mortgageValue;

		// assign var
		mortgageValue = document.getElementById('mortgageValue').value;

		// validate
		if (mortgageValue == "")
			{
			alert("Please enter your mortgage value.");
			return false;
			}

		// remove comma if exists
		if (mortgageValue.indexOf(",") > -1)
			{
			mortgageValue = mortgageValue.replace(",", "");
			}

		// test for numerics - having removed comma
		if (isNumeric(mortgageValue) == false) 
			{
			alert("Please enter numeric values only.");
			document.getElementById('mortgageValue').value = "";
			return false;
			}

		// test for mortgage value greater than £75,000
		if (mortgageValue < 75000) 
			{
			alert("We can only give a commisson cashback on mortgage values over \u00a375,000.");
			document.getElementById('mortgageValue').value = "";
			return false;
			}
		
		// validation ok - send calc request
		var xmlHttp;
		if (window.XMLHttpRequest) {xmlHttp=new XMLHttpRequest();}
		else if (window.ActiveXObject) {xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");}
		else {alert("Your browser does not support AJAX!");}

		// init url var
		var url;

		// construct url
		url = "calculateCashback.php?mortgageValue=" + mortgageValue;
		if (mykey) {url += "&mykey=" + mykey;}

		xmlHttp.onreadystatechange=function() {if (xmlHttp.readyState == 4) {document.getElementById("homeCashbackCalculatorAjaxUpdate").innerHTML = xmlHttp.responseText;}}
		xmlHttp.open("GET", url, true);
		xmlHttp.send(null);
		}

	return false;
	}

function recalculate(mykey)
	{
	// validation ok - send calc request
	var xmlHttp;
	if (window.XMLHttpRequest) {xmlHttp=new XMLHttpRequest();}
	else if (window.ActiveXObject) {xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");}
	else {alert("Your browser does not support AJAX!");}

	// init url var
	var url;

	// construct url
	url = "calculateCashback.php?act=recalculate";
	if (mykey) {url += "&mykey=" + mykey;}

	xmlHttp.onreadystatechange=function() {if (xmlHttp.readyState == 4) {document.getElementById("homeCashbackCalculatorAjaxUpdate").innerHTML = xmlHttp.responseText;}}
	xmlHttp.open("GET", url, true);
	xmlHttp.send(null);

	return false;
	}