I dont know what i missing here, using this for join:

But it triggers even due the user have other levels, it even trigger on me when i join with lvl 999.

Are your user levels correctly formatted?
See /help User List
You may be using the first level incorrectly.

I adding the user with: .auser 3 $address($1,3) .

If you want the event to only trigger for the specified user level use the + prefix.

Just to explain Deega's post in more detail...

By default, when you specify a userlevel number it will trigger the event for everybody on that level or lower, so, for example, on 3:join: would trigger for levels 3, 2 and 1. on 5:join: would trigger for 5, 4, 3, 2 and 1.

The + prefix makes it ONLY match the specified userlevel.

Somewhat related is the fact that using on 1:join: will only match people who either aren't in your user list or have a numbered user level; it won't match somebody with a named user level. To match *everyone* you should use *, like so: on *:join:.

I know this, but it dont explain why it trigger on lvl 999, thats "my" level. I only have my nick added as lvl 999 no need for host since no one can steal my nick when i have it, and the match for lvl 3 using the users host.

Your level 999 is higher than 3. Users can access any events matching or less than their access level, noting that only the highest matching event is triggered.
on 3:event: <- This triggers for all users with a level of 3 or greater.
on +3:event <- triggers for ONLY users with level 3


Edit:
You can also prevent level 999 users from triggering it by adding their level at "=999" which gives that user access only to level 999 events.

Actually the other way around, level 3 events match for anyone with an access level of 3 or greater.
on 5:join: would trigger for acess levels 5, 6, 7, .... 999. Not for 4, 3, 2, or 1.

Of course, my bad. Getting rusty!