function updateText (num) {
	var myElement = document.getElementById("calculatorGrams");
	myElement.value = myElement.value += num;
}

function checkform ( form )
{
  if (form.firstName.value == "") {
    alert( "Please enter your first name." );
    form.firstName.focus();
    return false ;
  }
  if (form.surname.value == "") {
    alert( "Please enter your surname." );
    form.surname.focus();
    return false ;
  }
  if (form.email.value == "") {
    alert( "Please enter your email address." );
    form.houseNum.focus();
    return false ;
  }
  if (form.town.value == "") {
    alert( "Please enter your town." );
    form.town.focus();
    return false ;
  }
  if (form.postcode.value == "") {
    alert( "Please enter your postcode." );
    form.postcode.focus();
    return false ;
  }
  if (form.email.value == "") {
    alert( "Please enter your email address." );
    form.email.focus();
    return false ;
  }
  if (form.email2.value == "") {
    alert( "Please confirm your email address." );
    form.email.focus();
    return false ;
  }
  if (form.mobileNum.value == "") {
    alert( "Please enter your mobile number." );
    form.mobileNum.focus();
    return false ;
  }
  return true ;
}