Actually it's the delevent.exe file you need. For multi-part scenarios with different event files you "wash" the savegame file with delevent.exe to remove the embedded events data. Then when you change the events file and reload, the new events are used.
What most people - in fact, I think everyone since multi-part scenarios were first used - have created a little batch file to automate this procedure. Red Front/Second Front are good examples.