I haven't tested your code, sner, but a few things I noticed.
1) When posting code, please use the Code Tags (which looks like the # character)
2) Usage of GOTO, while available, is, generally, not recommended
3) Usage of HALT statements, again, generally, is not recommended
4) I was unable to find the $parms identifier in the help file (this may be an old identifier, and may not work with up-to-date versions of mIRC)

Here's a suggestion for a re-write of your supplied code
Code:
on @*:text:*:#:{
  if $nick !isreg $chan {
    if $len($1-) < 330 {
      unset $+(%,tf,$address)
    }
    else {
      inc -u5 $+(%,tf,$address)
      kick $chan $nick Please don't flood
    }
  }
}