Control with "popup"

[Guest_imported]

Hi
I'm trying to build a control with a kind of popup, that appears when the user clicks the area of the control, like a combo box: one parte is always visible, when another can be visualized only if a particular area of the control il clicked.
I've tryed to put in the project a base control and a form, this one to simulate te popup.
The problems are:
1) The popup is a form, so a window. So, when it appears (Show method) it gets the focus (a combo box, when is opened, it doesn't get the focus for the popup). What I have to do, or which kind of object I have to use to avoid this?
2) Situation: the popup is opened, but the user selects another windows, or opens a menu. This should cause the popup to disappear. How can I do this?
3) The control got the focus and the windows where is located is the active window. The user select and active another window. So, the control should loose the Focus Rectangle (I have to redraw the control). How can I be informed that the window with my control isn't the active one anymore?

Thanks very much fo the help
Ciao
Dnì