var rand_no = Math.ceil(90000*Math.random() + 9999)

function validate_required(field,alerttxt)
{
with (field)
{
if (value==null||value!=rand_no)
  {alert(alerttxt);return false;}
else {return true}
}
}
function validate_form(thisform)
{
with (thisform)
{
if (validate_required(captcha,"Incorrect code entered!")==false)
  {captcha.focus();return false;}
}
}