If you are talking about the future and not the past, it might be easier to log it yourself into a seperate table you create. This extra insert would be more than offsett by the overhead caused by the event monitor.
I don't know what query mechanism you are using (such as a third party tool) but if you can run a script or procedure then it can contain the regular query and also SQL insert statements to log the information you want.
Have the script or procedure contain 3 SQL statements. The first is an insert (into a table you create) to log the start of the query. The next query is the regular query that is always run. The last insert would be to log the end of query execution.
There is also a program called db2batch that is supplied with DB2 to provides information in the output about how long it took to execute the SQL statement. This program was specifically designed for use in benchmarking.