function isNumeric(e) {

  if (e.keyCode) code = e.keyCode;
  else if (e.which) code = e.which; // Firefox
  else if (e.charCode) code = e.charCode; // Mozilla

  if ((code < 48 || code > 57) && (code != 13) && (code != 8)) {
    if (window.event) //IE 
	{
      e.returnValue = false;
    }
    else //Firefox 
	{
      e.preventDefault();
    }
    return false;
  }
  else {
    if ((code == 13))  {
      var vweight = document.getElementById("weight").value;
      if ((vweight > 0)) {
        calc_price();
      }
      else {
	    alert ('Please enter the weight of your Gold!');
      }
    } 
    else {
      return true;
    }	
  } 

}

function calc_price() {
  
  var vcarat = document.getElementById("carat").value;
  var vweight = document.getElementById("weight").value;
   
  var pos_1 = vcarat.indexOf ('-');
  var pos_2 = vcarat.indexOf ('*');
  
  var price        = vcarat.slice((pos_1+1), (pos_2) );
  var price_number = price * 1;
  var total        = price * vweight;
  
  
  var carat_type = vcarat.slice((pos_2+1));
  
  if (vweight=="") {
    
    document.getElementById('gold_carat').innerHTML = 'Our current price for ' +  carat_type + ' ct. gold is';
    document.getElementById('gold_price').innerHTML = '&pound;' + price_number.toFixed(2) + ' per gram';
    
  }
  else {
  
    document.getElementById('gold_carat').innerHTML = 'The value of your gold is';
    document.getElementById('gold_price').innerHTML = '&pound;' + total.toFixed(2);
  
    var calc_carat = vcarat.slice(0,pos_1);     
        
    //Add values in the IFRAME
        
		
    //var name_frame = document.getElementById("blockrandom");
        
    //calculate_weight
    //var calculate_weight = name_frame.contentWindow.document.getElementById("calculate_weight");  
    //calculate_weight.value = vweight;
        
    //calculate_carat
    //var calculate_carat = name_frame.contentWindow.document.getElementById("calculate_carat");  
    //calculate_carat.value = calc_carat;
        
    //calculate_value
   // var calculate_value = name_frame.contentWindow.document.getElementById("calculate_value");  
   // calculate_value.value = total.toFixed(2);
   //     
    //calculate_value_carat
   // var calculate_value_carat = name_frame.contentWindow.document.getElementById("calculate_value_carat");  
   // calculate_value_carat.value = price_number.toFixed(2);
        
  }
}