I wouldn't go for the while loop route like venom suggested, since the didtok is available at your disposal.

but a list of nicknames is NOT readily available at your disposal, you have to construct the list first. this really is overkill when you can simply add the nick straight to the listbox as venom showed.

you can also use:

/filter -wol #channel <dname> <id>

to get the nicklist of #channel in a dialog control. this also copies nick prefixes, however, which might be desirable in this case.