function calcvat() {
// calculates the VAT, Net and Gross values from a form
   for (j=0,m=document.vatform.elements.length;j<m;j++)
      if (document.vatform.elements[j].name == 'startingfigure')
         var startingfigure = document.vatform.elements[j].value;

   for (j=0,m=document.vatform.elements.length;j<m;j++)
      if ((document.vatform.elements[j].name == 'vatincluded') && (document.vatform.elements[j].checked))
         var vatincluded = document.vatform.elements[j].value;

   // Error checking
   var isvalidnum = true;
   startingfigure=startingfigure.replace("£", "");
   for (i=0; i<startingfigure.length; i++) {
      if ((startingfigure.charAt(i) != "0")
      && (startingfigure.charAt(i) != ".")
      && (!parseFloat(startingfigure.charAt(i)))) {
         isvalidnum = false;
         alert("Please enter a valid number in the 'Starting Figure' field");
         break;

      }
   }
   if (isvalidnum) {
   // Calculations
   startingfigure = parseFloat(startingfigure);
   if (vatincluded == "yes") {
      // New VAT Rate 20% 4/1/2011
      var vatout = startingfigure*(1/6);
      // Old rate 17.5% re-instated 1/1/2010
      //var vatout = startingfigure*(7/47);
      // Tmp rate 15% var vatout = startingfigure*(3/23);
      var grossout = startingfigure;
      var netout = grossout - vatout;

   }
   else {
      //var vatout = startingfigure*0.15;
      var vatout = startingfigure*0.200;
      var grossout = startingfigure+vatout;
      var netout = startingfigure;
   }

   // output values
   for (j=0,m=document.vatform.elements.length;j<m;j++)
      if (document.vatform.elements[j].name == 'netamount')
         document.vatform.elements[j].value = poundsandpence(netout);

   for (j=0,m=document.vatform.elements.length;j<m;j++)
      if (document.vatform.elements[j].name == 'vatamount')
         document.vatform.elements[j].value = poundsandpence(vatout);

   for (j=0,m=document.vatform.elements.length;j<m;j++)
      if (document.vatform.elements[j].name == 'grossamount')
         document.vatform.elements[j].value = poundsandpence(grossout);
   }
}
function poundsandpence(numnotrounded) {
// makes number conform to pounds and 2 decimal (pence) digits
var decbit = (numnotrounded.toString()).split(".");

if (!decbit[1]) var wholebit = decbit[0]+".00";
else if ((decbit[1].length) == 1) var wholebit = decbit[0]+"."+decbit[1]+"0";
else if ((decbit[1].length) == 2) var wholebit = decbit[0]+"."+decbit[1];
else {
   var tempbit = (Math.round((decbit[1].substring(0,2))+"."+(decbit[1].substring(2)))).toString();
   if (tempbit.length == 1) tempbit = "0"+tempbit;
   var wholebit = decbit[0]+"."+tempbit
}
return wholebit;

}