function updateCart()
{
   var p = 3;
   var gt = 0;
   for (var i=0; i<p; i++)
   {

      var q = iv(domID('q'+i).value);
      if (q<0)
      {
         domID('q'+i).value = 0;
         q = 0;
      }
      var t = q * domID('p'+i).value;
      domID('t'+i).innerHTML = '$'+ nf(t);
      gt += t;
   }
   domID('gt').innerHTML =  '$'+ nf(gt);
   domID('gst').innerHTML =  nf(gt/11);
}

function iv(x)
{
   p = new RegExp('[^0-9 ]');
   if (x.toString().match(p))
      return 0;

   if (x.toString().length>1)
   {
      var p = new RegExp('^[0]+');
      return parseInt(x.replace(p));
   } else if (x.toString().length==0)
      return 0;
      
   return parseInt(x);
}

function nf(x)
{
   var ip = Math.floor(x);
   var fp = x - ip;
   if (fp==0)
      return ip +'.00';
   else
      return ip +'.'+ (Math.round(fp*100));
}

function domID(i)
{
   if (document.getElementById)
      return document.getElementById(i);
   alert(i +' not found');
   return false;
}