Works on the combination of an event and station. Existing subsetters check on things like the station's distance from the event and things like that.
For more information on externals, see the externals documentation
<externalEventStationSubsetter> <classname>edu.somewhere.seis.sodExt.subsetter.eventStation.MyEventStationSubsetter</classname> </externalEventStationSubsetter>
In eventStation there is a choice between all of the following