IF argument for [...]

i tried this:

      if (strlen($thread[pagetext]) > 100) {
        $thread[message]=substr($thread[pagetext], 0, 95).'[high][...][/high]';
      } else {
        //$thread[message]=bbcodeparse($thread[pagetext],$forum[forumid],1);
        $thread[message]=$thread[pagetext];
      }
      if [high](condition)[/high] {
        $thread[message]=[high](here is my prob)[/high]
      } else {
        $thread[message]=preg_replace("/\[[^\]]*\]/","",$thread[message]); 
        $thread[message]=str_replace("\"","",$thread[message]);
      }

this will prevent to load the BBcode in the text i want to show. however, i have the [high][...][/high] code segment that will be removed also. an easy fix is to replace the brackets like that:
(...)

is there a way to keep the [...] format with an IF argument? thanks.