Hi,
I am finding it a bit hard to answer, as I don't underderstand the scenario.
I guess that you mean that you are trying to simulate an event driven system. If you wrote the code of the event system, to simulate an event on demand, just send that event using the normal API's (if possible) or you might need to use relection to call private methods.
If the event system is highly coupled with other systems that you don't really want you can use TypeMock.NET to mock those other systems.
Can you post a sample scenario?