Yes, that sounds right, although you could write the script to simply automatically check the ListMail database, lm_users table, for a "Removed" user by looking for "cnf" with a value of "0".
If placed in the ListMail folder you can have the database connection created by admin.php
<?phpinclude('./config.php');include('./admin.php');list($found)=@mysql_fetch_row(mysql_query("select id from $utable where list = '".addslashes($list)."' and email like '".addslashes($email)."' and cnf = '0';"));if($found){ // user was removed, forward to error page or exit('no can do');} else { // not found removed, continue to signup // signup - currently this supports only 3 custom fields header("Location: ./signup.php?list=$list&email=".urlencode($email)."&fname=".urlencode($fname)."&lname=".urlencode($lname)."&user1=".urlencode($user1)."&user2=".urlencode($user2)."&user3=".urlencode($user3));}?>
Regards