Forms in Flash - Basics

I’m experimenting with Forms in Flash (8 Pro) and my problem is, I’m sure, VERY BASIC. I create a new Form Application and get a top level called “Application”. I add 2 sibling forms under that (form1 & form2) and a child form under form1 called form3. If I add a button to form3, it appears on all other forms but I don’t want that. I understand that the top level (Application) is the receptacle for everything, so I might expect such thing to appear there but I want all other screens to have a unique appearance (though possibly a common look & feel template). How do I achieve this?