There are several already written programs to analyze weblogs (and/or ftp logs written in the weblog style).
Webalizer is one of them (source/binaries forr multiple platform):
http://www.mrunix.net/webalizer/
Take a look at the download page as well. There's a (small) 'related project' section, among other things.
To answer the question about the 'write every 2 minutes', I don't think that's possible. The logging is (near) real-time.
You can however manipulate who takes care of the actual logging. Piping it to a self written script/program is possible:
http://httpd.apache.org/docs-2.0/logs.html#errorlog
http://httpd.apache.org/docs-2.0/mod/core.html#errorlog
Damn..... I should read better, you're using 1.3. Here are the 1.3 versions, they are almost the same.
http://httpd.apache.org/docs/logs.html#errorlog
http://httpd.apache.org/docs/mod/core.html#errorlog