SetForegroundWindow is supposed to steal focus and there are certain cases where it will fail.
The SetForegroundWindow function puts the thread that created the specified window into the foreground and activates the window. Keyboard input is directed to the window
Try capturing the focus with SetCapture prior to making the call. Also look into different ways of bringing the window to the front: SetForeGroundWindow, SetActiveWindow, even simulating a mouse click can do this.