I would use a custom PHP script, but it might be possible with some advanced SQL.
e.g. (untested):
<?php// remove users on list y who exist on list x// example to purge list y users who exist on list x$listx = '2';$listy = '1';$pathtoLM = "./";include($pathtoLM.'config.php');include($pathtoLM.'admin.php');$xusers = mysql_query("select email from $utable where list = '$listx';");while(list($e)=mysql_fetch_row($xusers)){ $yuser = mysql_query("select id from $utable where list = '$listy' and email like '$e';"); if(@mysql_num_rows($yuser)>0){ list($yi)=mysql_fetch_row($yuser); mysql_query("update $utable set cnf = '2' where id = '$yi';"); echo "removed $e from list $listy<br>"; flush(); }}?>
Copy the code into a new .PHP file, modify the list numbers at the top, upload the file to your ListMail folder and browse to it.
Let me know if it works. :)
Regards