Set Focus on a child movieclip

Hi

I am able to setFocus on a Child Movie clip but cannot disable the parent from Actions. The requirement is : I have a login screen interacting with the DB. IF the user is not present a dialog box pops up. I am able to set the Focus on this Dialog Box. But when i go out of the Dialog box and click on the Main/parent screen which is behind the Dialog box it is accepting. I want to disable any event in the Login screen, excepting the Dialog box.
Please help…