InputControllerWin32 Mouse wheel

[Floady]

When the mouse wheel value is updated, you probably also want to set the flag

 case WM_MOUSEWHEEL:
            // Update member var state
            m_MouseState.WheelDelta = (float)((short)HIWORD(wParam)) / (float)WHEEL_DELTA;
            m_MouseState.ButtonFlags |= MouseState::BUTTON_FLAG_WHEEL;
            MsgHandled              = true;
            break;

[TheMostDiligent]

It is probably not necessary. The flags are used to detect when L/B/R mouse button is pressed and released. For the wheel, the WheelDelta already conveys the information.
Your change will set the BUTTON_FLAG_WHEEL flag, but it will never be cleared and will always remain set.