Oops, I forgot to mention something important about $ial, for the benefit of others reading the thread. mIRC doesn't offer the option to fill the ial with the members of channels after you join them. "hint hint"
First, you should make sure the IAL is turned on, which it is by default unless you turn it off. the "/ial" command without any parameter shows the on/off state, and you can use "/ial on" to turn it on if it's not already there.
By default, the $ial contains only the nicks of people in channels you're in. So even yourself isn't in your $ial list until you join a channel. Once someone in a channel does something, like joins, sends a message to channel, changes nick, etc - that nick is added to your IAL. But everyone idling in channel isn't in your IAL until you do something which causes them to be added. One thing you can do is to /whois them, but that would be a pain to do that for everyone else.
What you can do is "/who #channelname", which adds everyone who's not already there. It also does things for people already in your IAL list, such as updating their status as being marked as /away or not. You'd need to be careful about having a script which does the /who #channel shortly after you join, because if you join several large channels immediately after joining the network, the barrage of server replies can cause you to be flooded off as soon as you join, and would repeat each time you reconnected and rejoined those channels.