>I want to enable SDI in my application (could be a nice way to enable multi-session support).
>The ShowWindow property of my main form therefor is 2 - As top level form. The ShowWindow property of my other forms are set to 1 - In top level form.
>So far so good.
>I used to let users know where they are (navigation indicator) by displaying certain info in the header of the main form.
>To do so i used _screen.caption.
>My question is:
>HOW CAN IK REFER TO MY MAIN FORM (_vfp/_screen/application all point to the main visual foxpro window which is hidden in my case).

As long as child forms know about parent, just refer to the top-level:

topform.caption = "I'm in child form X"