lHand = FindWindowEx(Form1.hwnd, 0&, "WMPVideoWindow", vbNullString)
This requires a separate playback window. If it is used in a certain window, it will not be found.
Put the WindowsMdeiaPlayer control in a form Form1, use the API function GetClassName(Form1.hWnd, GetClassBuf, 256) to find the class name, and you can find the hWnd of the WindowsMdeiaPlayer control.