В чём ошибва при установке ловушки?

HookHandle = SetWindowsHookEx(WH_MOUSE_LL, reinterpret_cast<HOOKPROC>(Processing), hinstance, 0);

LRESULT CALLBACK Processing(int code, WPARAM wParam, LPARAM lParam)
{
if (code < 0)
return CallNextHookEx(HookHandle, code, wParam, lParam);
POINT MousePos;
GetCursorPos(&MousePos);
switch (wParam)
{
case WM_LBUTTONDOWN: break;
case WM_LBUTTONUP: break;
case WM_RBUTTONDOWN: break;
case WM_RBUTTONUP: break;
case WM_MOUSEMOVE: break;
default: wParam = 0;
}
return CallNextHookEx(HookHandle, code, wParam, lParam);
}