SiteInitializedEvent

I have a workflow that runs at startup and takes a parameter from a url query string and it's working fine. What I want to do now is let the user have the option of starting the workflow from the I want to menu and capture a geometry instead of taking the query string without creating a new workflow.

So what I was thinking is if I can capture the SiteInitializedEvent then I can use the query string from the url, and when the user starts the workflow from the I want to menu, it would by go to capture geometry.

I tried using the ListenForExternalEvent to capture the event and then using the CollectExternalEventArgs, but that's where I get stuck...how do I pass the initialized value "True" to a string for example.

Has anybody tried this?

Thanks

Pablo