How to Block only child window in Mdi Form Application.

Hi, every body.

everyone known that window.alert method in a web page will block all windows in microsoft IE, following screen capture show this case

recently, i find a Web Browser Has a different behavior, it just block the current page that shown the message box only, but not block other child pages, they can be click also.

let us see following capture.

So.

How can i get this  in my Mdi Form application, when a child form show modal dialog ,the dialog only block current child form ,but not block others child form and parent form,

if don't use MDI parent form ,i can use new thread STA to run a new message loop form every child form,

but use MID Parent Form , i can't combin all form in a Parent Form across Thread.

is there anybody give me some idea?

thanks advance.! 

DON'T TRY SO HARD,THE BEST THINGS COME WHEN YOU LEAST EXPECT THEM TO.