DHTML - fire event handler

Question

I have hosted a web browser and parsed through the DOM for a particular html page using mshtml interfaces to get to the following point: I have a handle to an HTMLInputElement and am trying to manually fire off the event handler tied to its onkeyup event. The HTMLInputElement has a public property 'onkeyup' that is returned as an Object (COM). From all the documentation I have read, it seems as if this object is the actual handler for the event. I do not know how to access it, though, so that I can manually fire off the handler (which is a javascript function returned in the html page). Anyone have any ideas?