$ialchan
From Scriptwiki
Returns the Nth address on the specified channel matching nick or mask in the Internal Address List.
$ialchan(nick/mask,#,N)
This identifier is basically the same as the $ial-identifier. The only difference is that it onyl returns matched for specified channels.
Note that N is not optional, contrary to $ial.
Example
echo -a $ialchan(*Dana@staff.quakenet.org,#help.script,1).nick
This example will return Dana.
echo -a $ialchan(*Dana@staff.quakenet.org,#mIRC,1).nick
This one will return $null, as Dana isn't on #mIRC.