Way to tear down my Microsoft Explorer mouse without broking it

I need to tear down my mouse because of the middle button that does not respond properly any more. I'd like to try to change it but it seems there is no screw to do it cleanly...

The only hole that could give access to a screw is in the middle and the element that looks like a screw seems to be more a rivet. Anyway, I would be very surprised if that thing was able to keep the mouse closed, by itself.

Anybody could explain to me how to tear down Microsoft mice in general or maybe that one in particular ?

Thank you by advance.