This script extends the troop event system with "end phase triggers". This is simply a final check on all of the event pages when a victory/lose condition has been met. Any pages that can be run during this end phase will be executed and may change the outcome of the battle.
This script is completely plug-and-play and requires no additional setup.
Download
Get it at Hime Works
Usage
Plug and play. Just set up your events as usual.
Add-ons
You can use extended event page conditions with this script. More information at
http://www.rpgmakervxace.net/topic/4174-event-extend-page-conditions/
Basically, by combining these two scripts, you can have arbitrary page conditions. Now you can really run an event when "all enemies are dead" by simply writing