function validate_required(field,alerttxt)
{
with (field)
{
if (value==null||value=="")
  {alert(alerttxt);return false}
else {return true}
}
}
function validate_form(thisform)
{
with (thisform)
{
if (validate_required(client_first_name,"Please enter your first name")==false)
  {client_first_name.focus();return false}
if (validate_required(client_last_name,"Please enter your last name")==false)
  {client_last_name.focus();return false} 
if (validate_required(email,"Please supply a valid email address")==false)
  {email.focus();return false} 
}
}