simulate mouse click across application (win32)

[Sugree Phatanapherom]

I try to sendmessage across process to simulate mouse click but didn't
work.

wnd = win32ui.FindWindow(None,"PythonWin")
wnd.SetForegroundWindow()
win32api.SetCursorPos(100,100) # somewhere in windows
wnd.SendMessage(win32con.WM_LBUTTONDOWN,0,0)
wnd.SendMessage(win32con.WM_LBUTTONUP,0,0)

Any ideas?