Maybe mIRC should have a icon in the menu bar so that whenever the sever says "Target change too fast please wait for XXX secs" the mIRC will autojoin the channel after the time. Or maybe on the join channel icon allow the person to choose after how long the mIRC will auto-join the channel.
And for those newbie who thought that the mIRC got problem, because they might also get "Target change too fast" message, the mIRC will also help to re-msg the person automatically so that newbies don't have these trouble.
