Since a form is usually opened as the result of a process. (or it can be, so instead of having an action of "Create Object" which would open a form, have a process, that will do that), can't you handle the open stuff in this process.
On save, you have an option to have a process run after, so you could have this process capture more stuff.
How will this not work for you?
Now, what I REALLY REALLY want is an event when a TAB gets FOCUS. If I have multiple tabs open, I have no easy way to know when a user CLICKS on one of them. This would make my life a lot easier.
Bruce