Forums Scripts & Popups Listbox for channel window?

Trying to do a simple on join command to add a line to the listbox for that channel. I know this is handled elsewhere but I'm at a loss on this one.

//echo -a $fline( $+ $chan $+ , * $+ $nick $+ *, 1, 1)

Will look into the room listbox and find the matching nick, so I know it's not having a problem finding it (via the $chan window name) nor finding the proper nick.

But...
on *:JOIN:#: { aline -l 15 $chan $nick }
fails with * /aline: invalid parameters
on *:JOIN:#: { aline 15 $chan $nick }
fails with * /aline: insufficient parameters

If I do //echo $chan Test it outputs "Text" to the channel window.

I'm asuming there's some no-no about manually tinkering with the listbox for channel windows but I want to know how to get around that. Is this routine just hard coded to not allow it or is there some super secret formatting I should be using?

Thanks in advance.