Just put it in remote, and it'll do the work. There is just 1 warning, and after that a permanent kick/ban.
All the credits go out to 'tidy trax', user of the mirc forum.

p.s. If you want a temporarily ban, instead of these lines:
mode # +b $address $chan $nick You were warned
kick # $nick

You could use this line:
ban -ku60 $chan $nick You were warned

(For changing the time of the ban, change the number 60. (stands for seconds))

on $@*:text:/||/:#:{  
  if $nick isreg $chan {    
    hinc -m col $nick    
    if $hget(col,$nick) == 1 { msg # 0,1This is the first and only warning $nick $+ , do not use colours, underline or bold in this channel. Next time you will be banned.     }    
    elseif $hget(col,$nick) == 2 {       
      mode # +b $address $chan $nick You were warned   
      kick # $nick     
      hdel col $nick    
    }  
  }
}