Hi Poul,
showing a message, which basically just gives the user information and lets them select ok is fairly straight-forward.
Getting them to make a decision, and then changing behavior based on that decision is a lot more complicated because, there would then be multiple threads involved. Remember each thing the user does is a new thread, so the "save" would be one thread, and the message would be a whole other thread.
So perhaps, be more specific. In what circumstances do you want the user to do what. for example a "other" button on a form is very different to a "save" button on a form, and so on.
cheers
Bruce