I am just assuming few things before providing you my solution.
in reply to Parsing a specific section of a log file
Assumption 1:You are running this script on Unix/Linux,
Assumption 2:The log file gets appended from bottom
Script can save the latest log file to some other directory after every run. Then script will run system 'diff' command to find out differences between latest log file and your saved log file (Which is the last version of log file). You will get entries, which are latest addition after last execution time of script. Work on those entries and use regex your way.