Why not ban them using one of the wildcard masks, then don't remove the ban?
For more information on the options for the masks read /help $mask
The format to ban someone from a channel, using a specific mask is /ban <-k> #channel Nick <ban_mask>
the -k is only needed if the person is in the room and you want to kick them out using the same command.
<ban_mask> is a number from 0 to 19, which are documented in the mIRC help file under $mask