I have a window that is set with HWND_TOPMOST for its z position. And I want to be able to know when a window bellow it has been grabbed. The problem is that windows isn't sending a WM_CAPTURECHANGE message to my window when the lower windows is grabbed (since it is always lower in the z order). I tried having another thread keep track of the HWND of the window lower than mine and notify me when there is a change in HWND but that doesn't seem to work right. Am I even on the right track here. Is there a function that I don't know about?