function validate_required(field,alerttxt)
{
with (field)
{
  if (value==null||value=="")
  {
  alert(alerttxt);return false;
  }
  else
  {
  return true;
  }
}
}

function validate_number(field,alerttxt)
{
with (field)
{
  if (isNaN(value))
  {
  alert(alerttxt);return false;
  }
  else
  {
  return true;
  }
}
}

function validate_form(thisform)
{
with (thisform)
{
if (validate_required(quantity,"You must enter a quantity!")==false)
  {quantity.focus();return false;}
else if (validate_number(quantity,"Invalid quantity!")==false)
  {quantity.focus();return false;}
}
}