Shoutbox

I want to make a more visual method of creating windows in Interface Writer, and I need to know if I can get the width and height of a PlusWnd object.  I'm guessing that I would need to register the WM_SIZE notification on the window, and also that I would need to use Interop, but what function?

And also, can I set the width and height of the window?

Edit: is this on the right lines?