MDI form help

I have an MDI application where I am trying to stop users from opening the same children forms more than once. I have menu items and toolbar buttons that I disable when the child form is loaded and enable when the child form is unloaded. I would rather keep the buttons enabled and when the user clicks on a button for a child form that is already open, that child form would become active. In a way I want to replicate the actions of the "Windows" menu item in my parent container. Can someone please offer some advice?

Thanks