Keon191, use napa182's example above.

Change:> on !:JOIN:%greetchan:.timeropcheck 1 1 opcheck $nick #
alias -l opcheck if ($nick($2,$1,@)) .notice $1 7 $1 Welcome to $v2 11 Have a nice 7 Chat
on !:part:%greetchan:if ($nick(%greetchan,$nick,@)) .notice $nick 7 $nick You left from %greetchan 11 cu 7 laterThe @ means op. The bits I mark in red are where you can add more mode prefix to it.
If you only want this to work for ops or above when they join and part, add more as such:> if ($nick($2,$1,@&~))Otherwise, just use the single @ will do it.

Or I believe you can simply use this:

if ($nick($2,$1,a,hvr))

this will exclude halfop, vocied and regular users from being greeted.