Focus for Multiple Child Windows

Hi i have created my main window and then i create a few other standard windows using the main window as the parent. The problem I am having is that the child windows cant seem to get the focus properly (controls i add to these windows cannot be used). If i click any of the windows i can drag them and resize them but the title bar never goes blue to indicate it has the focus. I know that this problem can be solved by using the MDI (this is how we did it at the last place i worked) but i really dont want all the hassle of doing that. Any ideas?